T-cell
subsets in autoimmunity
Don Mason and Deborah Fowell MRC Cellular Immunology
Unit,
The demonstration
Sir William
that functionally
Dunn
different
by the isoforms of the leukocyte-common has prompted have
the ability
shown that diabetes
to inhibit
may
play
system
a role
too,
mediate
in the
it appears
of autoaggressive is evidence
CD45, that they express,
that
autoimmune enterotoxin
pathogenesis
that
subset of CD4+
disease.
this protection
Further,
suggesting
of this
that
disease.
experimental
in Immunology
Introduction Mechanisms mediating self tolerance
The issue of whether self tolerance depends entirely on the mechanisms of clonal deletion and T-cell anergy remains controversial. Although the existence of these mechanisms have been amply demonstrated, they fail to account for all experimental data on autoimmunity. If non-reactivity to self is entirely a consequence of an absence of self-reactive T cells then perturbation of the immune system, for example by neonatal thymectomy or adult thymectomy plus y-irradiation, should not lead to the development of autoimmune disease- but it does in a variety of experimental systems (reviewed in [1,2**] ). These findings have led to the conclusion that normal healthy individuals, with no evidence of organ-specific autoimmune disease, may possess autoreactive T cells that, for some reason, do not express their autoimmune potential. Studies of the response of different mouse strains to pathogenic organisms have shown that the outcome of an antigenic challenge is heavily dependent on genetic variation in the types of cytokine that are elicited by the pathogen in question. Susceptibility to LeiSwnmzia in Balb/c mice arises because the host makes an inappropriate immune response which suppresses the effective one [3**,4,5*]. The demonstration that cytokines can play such potent immunoregulatory roles in infectious diseases has naturally raised the question as to whether similar mechanisms may be involved in regulating autoimmune reactions, in this case to the benefit of the individual [ 2**], In experimental systems, where manipulation of the immune system results in the development of autoimmu-
superantigens in this
the induction diseases there
and that these cells may
by the synthesis of transforming
Opinion
it has been
However,
autoimmune
T cells can be protective
The T cells
by in vitro activation
a subset of T cells can inhibit
cells. In other CD8+
Current
of a particular
in the B-B rat can be transferred
of T cells by Staphylococcal
growth
factor-p.
1992, 4:728732
n&y, the manipulation always produces a degree of immunodeficiency. This fact has led to the proposal of two mechanisms for the breaking of self tolerance. Firstly, environmental antigens, normally eliminated by a competent immune system, can activate in the immunocompromized animal low affinity autoreactive T cells which then upregulate their adhesion molecules and thereby become autoaggressive [6]. These T cells are believed to escape intrathymic clonal deletion by virtue of their low alhnity. Secondly, the immune system possesses T cells that recognize self antigen and these T cells suppress other T cells with autoreactive potential. Note that the protective T cells, although possibly specific for the autoantigen, must be qualitatively different from those that cause disease. Evidence for the second of these two mechanisms can be found in earlier literature. For example, antibody to complement component C5 can be elicited in CS-deficient, but not CS-sufficient, congenic mice and T cells from the CS-sufficient animals can transfer resistance to autoantibody induction [7]. The suppressive T cells were apparently CD8+. Similarly, prostatitis (inflammation of the prostate gland), which developed spontaneously in mice thymectomized on day 3 after birth, was inhibited by a tenfold lower dose of T cells from normal syngeneic male mice than from female mice [8]. A recent paper supports the concept that autoreactivity may be prevented by immunoregulatory T cells that themselves recognize self antigen [S] In these experiments a CD4+ T-cell line, obtained from mice hyperimmunized with testicular germ cells and propagated in vitro by stimulation with mouse testicular antigen in the presence of cyclosporin A, was shown to inhibit the induction of experimental autoimmune orchitis (inflammation of the testis). Both cellular and humoral responses to the
Abbreviations IF&inteferon; 728
IL-interleukin;
UK
T-cell subsets can be defined
antigen,
studies on the roles of these subsets in autoimmunity.
results have led to the identification that
School of Pathology, Oxford,
TGF-transforming
growth factor; Th-T
@ Current Biology Ltd ISSN 0952-7915
helper.
T-cell subsets in autoimmunity
autoantigen were inhibited but the authors did not report on the cytokines produced by the protective cell line. It is evident that the two proposed explanations for the appearance of autoimmunity in relatively immunodeficient animals are not mutually exclusive. In principle, a deficiency of ‘suppressor’ cells could allow activation of low affinity clones to occur at the site of autoantigen expression. In this context , it has recently been reported that Staphylococcal enterotoxin activated spleen cells can passively transfer diabetes in the B-B rat but only if RT6+ CD4+ T cells, which previous studies have implicated in the prevention of diabetes in this rat strain, are excluded from the in vitro culture to which the superantigens are added [lo**]. This result, which resembles a previous one in which Con A was used in vitro to activate the T cells, will be discussed in more detail later in this review.
Subsets of CD4+
T cells
The classical division of lymphocytes derived from the thymus into CD4+ and CD8+ subsets is no longer an adequate indication of the heterogeneity of these cells. In man, mouse and rat, T cells, in particular CD4+ cells, have been shown to be heterogeneous with regard to the cytokines that they synthesize as clones [11*,12,13] and the isoforms of CD45 that they express when freshly isolated from donor animals [ 14.1 (for review see [ I5**]). These facts have led to an extensive study of the properties of these diierent subsets and, although these studies are far from complete, there is clear evidence that there is an association between the CD45 phenotype of a CD4+ T-cell subset before it is activated and the repertoire of cytokines that it secretes on activation [ 16*,17,18]. However, there is not a simple relationship between the type of T helper (Th) cell and CD45 isoform expression and it seems likely that the ThI celVTh2 cell dichotomy represents a terminal state of T-cell specialization [ 19.,20*]. In addition, given the number of known CD45 isoforms, there may be many more unique T-cell phenotypes than are currently identified. The recognition that CD4+ T cells are not functionally homogeneous has resulted in studies of the roles of their subsets in autoimmunity. The data, discussed below, indicate that a subpopulation of T cells with autoimmune potential exists but that these cells are controlled by a different subset of CD4+ T cells. These cells may provide their protective function by inhibiting T-cell activation by superantigens.
induce
subsets of CD4+ and prevent
T cells in the rat
and Fowell
received CD45RChigh CD4+ T cells developed mononuclear cell infiltrates in lung, liver, stomach and pancreas and a few rats also developed thyroiditis with anti-thyroglobulin antibodies. All of these rats died with a progressive wasting disease. In contrast, rats given the CD45RCIoW CD4+ T-cell subset remained well with no inflammatory cell infiltrates in any organ. More significantly, rats given unfractionated CD4+ T cells also remained well, indicating that the CD45RCkW cells in this inoculum somehow inhibited the pathology induced by the CD45RCh@ subset. Thoracic duct lymphocytes from all of these rats contained a high frequency of activated T cells but there was a notable difference in that recipients of the CD45RC1(lWCD4+ subset had T cells that, on isolation from the thoracic duct, were found to be expressing mRNA for interleukin (IL)-4 whereas recipients of CD45RChigh CD4+ T cells were not. This result is consistent with the known cytokine repertoires of these sub sets [ 171. Given the role of IL-4 in inhibiting cell-mediated immune responses and the demonstration that, in the rat, CD45RChigh CD4+ T cells on activation are more potent producers of interferon (IFN)-), and IL-2 than the corresponding CD45RCIOW subset (for review see [ I5**] >, [ 171, then the results obtained from the nude MS could be interpreted as the inhibition by the CD45RCIow subset of an autoimmune cell-mediated reaction produced by the CD45RChigh cells. In the second series of experiments in rats, autoimmune diabetes was induced in PVG.RTl” rats by adult thymectomy and repeated low dose y-irradiation [ 2**]. Diabetes and ins&is in these thymectomized and irradiated PVG.RTl” animals could be completely inhibited b! the intravenous injection of 5 x 106 CD45RCjoW CD4+ T-cell receptor aj3 + RT6+ Thy-l _ T cells from syn geneic donors. In contrast, cells of the CD45RChigh CD4+ phenotype did not protect against diabetes but caused a wasting disease similar to that seen in nude rats given cells of this type. Unfractionated CD4+ T cells were also protective but only in proportion to the CD45RC% cells in the inoculum. This result, like that with the PVG.RTl< nude rats given CD4+ T cells, showed that the protec tive effect of the CD45RCIoW subset was dominant over the pathological effect of the CD45RChigh one. These studies on diabetic rats are consistent with earlier, though less comprehensive, data showing that CD4+ T cells can prevent diabetes in NOD mice [ 21,22 1 and in B-B rats [23], In the latter case, the protcctivc c,rllq were shown to be RT6 +, as in the present experiments Activation
Different
Mason
of diabetogenic
Staphylococcal
T ceils by
enterotoxin
autoimmunity
Two studies of autoimmunity in rats have illustrated the role of different subsets of CD4+ T cells in the induction and prevention of autoimmunity. In the first of these, congenitally athymic (nude) PVG.RTlc rats were injected with CD4+ T-cell subsets from congenic euthymic donors [l]. The CD4+ cells were fractionated on the basis of the level of cell surface expression of exon C of the gene encoding rat CD45. Rats that
Depletion of RT6 + T cells from the diabetes-resistant subline of the B-B rat can result in the spontaneous devel opment of diabetes [24]. In a recent development of this experimental system it has been shown that splenocytes from diabetes-resistant rats, when activated in zdtm with various Staphylococcal enterotoxins, are able to transfer diabetes into young diabetes-prone recipients [lo**]. Interestingly, the adoptive transfer was successful only if the splenocytes were first depleted of RT6+ T cells by in z+z’o
729
730
Autoimmunity
treatment of the spleen donors with anti-RT6 monoclonal antibody. The authors suggest that RT6+ T cells inhibit the Staphylococcal enterotoxin induced activation of the diabetogenic T cells. This result is reminiscent of the protective effect of RT6+ T cells in vivo in both the B-B and the PVG.RTlu rats, however, whether superantigen plays a diabetogenic role in vivo remains to be determined. There is considerable literature on the effect of diet on the incidence of diabetes in the B-B rat but none is very conclusive. Possibly diet affects the intestinal flora in such a way as to promote or impede the production of bacterial superantigens. In this regard it is notable that the intestinal flora has been implicated in determining the incidence of autoimmune thyroidltis in rats [ 25.1. However, it has been reported that the incidence of diabetes in NOD mice is higher in germ-free animals [ 26,271. Thus, the effects of the environment appear complex especially [ 281. when data in man are also considered
Cytokines,
T-cell
subsets and autoimmunity
There are several recent publications which implicate cy tokines in the induction and prevention of autoimmune diseases. Consonant with the ability of IL-4 to inhibit cellmediated immune responses it has been shown that injection of this cytoklne can accelerate recovery from collagen-induced arthritis in mice [29’]. In addition, the treatment of NOD mice with anti-IFN-y antibody has been shown to protect the recipients from diabetes [30,31]. Given that IL-4 can inhibit the induction of IFN-)I [32,33] the result with the NOD mice is consistent with the observation that the subset of CD4+ T cells that prevents diabetes in the lymphopoenic PVG.RTl” rats is the one that produces IL-~.
Other examples of the inhibition of autoimmunity by CD8+ T cells have been reported. Certain CD4+ T-cell lines, specific for myelin basic protein, can elicit experimental allergic encephalomyelitis in Lewis rats. These arimals develop a single episode of disease and are then refractory to further challenge. This refractory phase appears to depend on CD8+ T cells that are specific for the particular CD4+ T-cell line used in the primary challenge. In a recent paper it is reported that neonatal exposure of Lewis rats to a CD4+ encephalitogenic T-cell line abrogates the development of the refractory phase in these rats when they become adults. The abrogation is specific for the CD4+ T-cell line injected neonatally [40]. The authors conclude that the neonatal exposure renders the rats tolerant to the encephalitogenic line so that immunoregulation, mediated by line-specific CD8+ T cells, no longer occurs. To what extent such an immunoregulatory mechanism is of physiological importance is not clear. Rats and mice depleted of CD8+ T cells do not generally develop autoimmune diseases but there is recent evidence that CD8+ T cells may inhibit autoantibody synthesis induced in BN rats by mercuric chloride treatment [41]. The mode of action is not known. Conclusion The conclusion that self tolerance depends, in part, on active T-cell mediated processes seems well founded. Although there is little understanding at present as to how these protective mechanisms work, there is evidence that certain subsets of T cells prevent autoreactivity, possibly by the secretion of particular lymphokines such as IL-4 or TGF-p. Acknowledgements
There have been a number of studies relating abnormal T-cell subset composition in peripheral blood to human autoimmune disease. In the most recent of these it has been shown that patients with mixed connective tissue disease have an abnormally high proportion of CD4+ T cells of the CD45RA+ phenotype [34]. This result resembles that found in an earlier study of insulindependent diabetes where a similar imbalance was reported [35]. The functional significance of these findings remains to be determined.
CD8+
T cells that prevent
autoimmunity
The observation that oral administration of antigen primes Peyer’s patch T cells for a Th2-cell type response [36-I with a high level of IL-5 (and presumably IL-4) production may provide an explanation for the recent demonstration that feeding NOD mice porcine insulin delays the onset and reduces the incidence of diabetes [37]. However, there is evidence that the inhibition of autoimmunity induced by oral tolerance is mediated by transforming growth factor (TGF)-fi produced by CD8+ T cells [38**]. It has also been shown recently that CD8+ T cells can produce IL-4 on appropriate stimulation [39*-l but whether this observation is relevant to oral tolerance is not known.
It is a pleasure
to acknowledge past and present members of the Cellular Immunology Unit that have contributed to these studies, in particular, Andrew McKnight, Fiona Powrie, Neil Barclay and Steve Simmonds.
References
and recommended
reading
Papers review, . ..
of particular interest, published have been highlighted as: of special interest of outstanding interest
within
the annual
period
of
I.
POWRIE F, MASON DW: ox-22high CD4+ T Cells Induce Wasting Disease with Multiple Organ Pathology: Prevention by the OX-22tow Subset. J Eq Med 1!990, 172:1701-1708.
2. ..
FOWELLD, MCKNICH~ AJ, POWRIE F, DVKE R, MASONDW: Subsets of CD4+ T Cells and their Roles in the Induction and Prevention of Autoimmunity. Immunol Rev 1991, 123376% The detailed characterization of the CD4+ T~ceII subset that, on isolation from healthy donors, prevents the development of cell-mediated autoimmune disease. Cells of this phenotype provided secondary B-cell help and on activation produced IL-4. 3. ..
UXKSIEY FCM,HEINZEL FP, HOLADAYBJ, MUTHA SS, RHNER SI., SADICKMD: Induction of Thl and Th2 CD4+ Subsets during
Murine Leishmania Major Infection. Res Immunol 1991, 142:28-32. A valuable review of the roles of IL-4, IFN-y and tumor necrosis factor-a in determining the outcome of Leisbmania infection in different mouse strains.
T-cell
4.
SCOT P: Host and Parasite Factors Regulating the Development of CD4+ T-cell Subsets in Experimental Cutaneous Leishmaniasis. Res Immunol 1991, 142:32-36.
subsets
in autoimmunity
Repertoire of Subsets 1991, 21:1187-1194.
T Cells.
and Fowell
Eur J Immunol
5. .
LFE WT, YIN XM, VITE-ITAES: Functional and Ontogenetic Analysis of Murine CD45Rhi and CD45Rlo CD4+ T Cells. J Immunol 1990, 144:328%3295.
6.
MOSMANNTR: Cytokine Secretion Phenotypes of TH Cells: Res Immunol How Many Subsets, How Much Regulation? 1991, 142:‘+13. An update on the classification of CD4 + T~cell clones into Thl~ and ThZ-cell types indicating that intermediate types also exist.
a Th2 CHATEWN R, VARKI!.AK, COFFMAN RL: IL-4 Induces Response in Leishmania Major-infected Mice. J Immunol 1992, 148:1182-1187. A clear in viva demonstration of the ability of IL-4 injected into mice to inhibit a cell-mediated immune reaction, whilst failing to establish a stable ThZ-cell response in a Thl~type responder mouse strain. SIEGEL KM, KATSUMATA M, KOMOR~ S,
WADSWORTHS, GILL-M•RSI; I., JERROID-JONESS, BHANI~LA A, GREENE MI, Y~JI K: Mechanisms of Autoimmunity in the Context of T-cell Tolerance: Insights from Natural and Transgenic Animal Model Systems. Immunol Rev 1990, 118:165-192.
7.
CAIRNSI., ROSEN FS, BORELy: Mice Naturally Tolerant to C5 have T Cells that Suppress the Response to this Antigen. Eur J Immunol 1986, 16:1277-1282.
8.
TAGUCHI 0, NISH~ZUKA Y: Self Tolerance and Localized Immunity. Mouse Models of Autoimmune Disease that Suggest Tissue-specific Suppressor T Cells are Involved in Self Tolerance. J Exp Med 1987, 165:146156.
9.
ITOH M, MUKASAA, TOKIINAGAY, 111~4~1~~ C, HOJO K: Suppression of Efferent Limb of Testicular Autoimmune Response by a Regulatory CD4+ T CeU Line in Mice. Clin Exp Immunol 1992, 87:455460.
10 ..
K.E, IJKE AA: Staphylococcal Enterotoxin-activated Spleen Cells Passively Transfer Diabetes in BB/Wor Rat. Diabetes 1992, 411527-532. Reports that ubiquitous superantigens may play a role in the activation of autoimmune T cells in diabetes. Also a useful source of references on superantigens.
DEL PRETE G~F,
DE
CARU
M,
MA~TROMAIJRO C,
BL&K)TII
R,
D, FALAG~ANIP, RICCI M, R~MAGNANI S: Purified Protein Derivative of Mycobacterium Tuberculosis and Excretory-Secretory Antigen(s) of Toxocura Canis Expand In Vitro Human T Cells with Stable and Opposite (Type 1 T Helper or Type 2 T Helper) Profile of Cytokine Production. J Clin Invest 1991, 88:346350. MACCHIA
13.
19. .
ANDEFSWN J, ANDERSSOX II: Assessment of Cytokines by Immunofluorescence and the Paraformaldehydesaponin Procedure. Immunol Ret’ 1991, 119:6>93. An elegant study of cytokme synthesis of uncloned human T cells show ing, for example, simultaneous synthesis of IL-4 and IFN-y by a smgle cell
20. .
SANDER B,
21
Hutchings PR, Cooke A: The Transfer of Autoimmune Diabetes in NOD Mice can be Inhibited or Accelerated hy Distinct CeU Populations Present in Normal Splenocytes Taken from Young Males. ,I Autoimmun 1990, 3:175P185.
22.
BOITARD C, Y.~_SINAMI
25.
MOSMANNTR, COFFMANRL: Thl and Th2 Cells: Different Patterns of Lymphokine Secretion Lead to Different Functional Properties. Ann Rev Immunol 1989, 7:14>173.
24.
MA.SOND: Subsets of CD4+ T Cells Defined by their Expression of Diierent Isoforms of the Leukocyte-common Antigen, CD45. Biocbem Sot Transactions 1992, 20:18%190. A concise account of the expression of various CD45 isoforms by CD4+ T cells of the human, mou.se and rat, and how this expression changes with maturation, differentiation and activation. EAR AN, SALMON M, IVORY K, TAKI S, PILLING D, JANOSSY G: Human CD4+CD45RO+ and CD4+CD45RA+ T Cells Synergize in Response to Alloantigens. Eur J Immunol1991, 21~2517-2522. The demonstration that on activation in vitro CD4+ CD45RA+ T cells produce IL-2 only but that CD4+ CD45RO+ cells have a wider cytokine repertoire, consistent with them being previously primed in oivo. MCKNIGHT AJ, BARCLAYAN, MACON DW: Molecular Cloning of Rat Interleukin 4 cDNA and Analysis of the Cytokine
“1.
DL, MOR~ESJP. HANDLEKES, ANGELILLOM. N&%%MI n4 N, ROSSINIAA: Depletion of RT6.1+ T Lymphocytes Induces Diabetes in Resistant Biobreeding/Worcester (RR/W) Rats. .I Eq Med 1987, 166:461475. PENHALE WJ,
YOTING PR: The Influence of the Normal Microbial Flora on the Susceptibility of Rats to Experimental Autoimmune Thyroiditis. Clin Exp fmmrw/ol 1988. 7228x-292. A report that rats reared in specific pathogen free conditions have :I low incidence of experimental allergic thyroiditis but convert to high incidence when exposed to the intestinal flora of rats reared in nclnspecific pathogen free conditions.
26.
WICKER
IS,
MILLER BJ,
COKEK
IZ,
MCNALLY
SE.
SLOTI
5,
MIII~~ Y, AIJI%L MC: Genetic Control of Diabetes and Insulitis in the Non-obese Diabetic Mouse. ./ lhp .Med 19X’. 165:163%1654. 27.
T, FUJIMLVA T, K4whw~4 E. SHI~UZI M R, NOMO’I’OK: Diabetogenic Effects of Lymphocyte Transfusion on the NOD or NOD Nude Mouse. In Immune- deficient Animals in Biochemical Resrurcb. Edited by Rygaard J, Dnmner N, Groem N, Spang~Thomsen M Basel: Karger; 1987:112-116. SUZUKI T,
YAMADA
YAMASHITA
28
Tonn JA: A Protective Role of the Environment in the Development of Type 1 Diabetes? Diabrtic .Ihd 1991. 8:90&910.
~WCEXI~I*I’ JF, I OfiARA J, K_41’% DH. Collagen-induced Arthritis in Mice. Relationship of Collagen-specific and Total IglSynthesis to Disease. J Immunof 1991, 147:41854191 Evidence is presented that the administration of IL~t ian dc,celerare ru covery from an experimental, cell-mediated, autoimmune disease. 29. .
30.
DEBRAY-SACI~S M,
C.~RNAUD C,
BOITARD C,
COHEN
H,
GIU’SSFR
JF: Prevention of Diabetes in NOD Mice Treated with Antibody to Murine IFN Gamma. I Autommun 1991, 4~237-248. 1, BELX%SA P, BACI~
16. .
17.
ES, GREINER DL. NhhAhlw\
GKEINER
25. .
.
15. ..
GAI.I.INA DL, 114~~1~~
MORDF.SJP,
Transfusions Enriched for W3/25 + Helper/Inducer T Lymphocytes Prevents Spontaneous Diabetes in the BBNli Rat. Diabetologia 1987, 3O:Z&26.
14.
WINGA J, GROEN H, KIATTER F, MEEDENDOWB, ASPINALL R, ROSER B, NIEWENHUISP: Postthymic T CeU Development in Rats: an Update. Biocbem Sot Transactions 1992, 20:191-197. Transplantation of primary vascularized thymuses in the rat have ens abled the detailed phenotyping of CD4+ T cells as they leave the thymus and during maturation in the periphery. In the rat, CD4+ cells that have recently migrated from the thymus are CD45RClow Thy-l+ RT6 and mature into peripheral (naive) CD45RC”gh Thy-l RT6+ T cells.
R, DARDI:UYFM, BACH JF, T CeU-mediated Inhibition of the Transfer of Autoimmune Diabetes in NOD Mice. J E.xp Med 1989, 169:166~1680.
PELLETIER A, R~SSINI AA:
EUEw
11. ROMAGNANI S: Human Thl and Th2: Doubt No More. Im. munol Today 1991, 12:256257. A summary of the evidence for functional specialization of human T cells. T~ceU clones with distinct Thl~ or ThZ-cell lymphokine profiles could be isolated from patients with different disease states. 12.
18.
of CD4+
Mason
31.
IL, KAY TW, OXBROW L, H.+wuso~ LC: Essential Role for Interferon-gamma and Interleukin-6 in Autoimmune Insulin-dependent Diabetes in NOD/Wehi Mice. J Clin Invest 1991, 87~739-742.
32.
PELEMANR, Wu J, FARGE.~SC, DELESPFSSEG. Recombinant Interleukin 4 Suppresses the Production of Interferon -/ by Human Mononuclear CeUs. J Exp .Wed 1989, 170:1751-1756.
CAMPBELL
731
732
Autoimmunitv
33.
GEHA RS: IL-4 Inhibits the Synthesis of IFN-y and Induces the Synthesis of IgE in Human Mixed Lymphocyte Cultures. J Immunol 1390, 144:570-573.
VERCELLI D, JABARAHH, IAUENER W,
34.
BECKER H, IANGROCK A, FEDERLIN K: Imbalance of CD4 + Lymphocyte Subsets in Patients with Mixed Connective Tissue Disease. CIin Exp Immunol 1992, 88:91-95.
35.
FAUSTMAN D, E~SENBARTH G, DAIEYJ, BREITMF(ER J: Abnormal
T-lymphocyte 38~1462-1468.
Subsets in Type 1 Diabetes. Diabetes 1989,
Xu-AMANO J, AICHERWK, TAGUCHIT, KXONO H, MCGHEEJR: Selective Induction of Th2 Cells In Murine Peyer’s Patches by Oral Immunisation. Int Immunol 1392, 4:433-445. Mice immunized orally with sheep erythroqtes were found to have a higher frequency of antigen-specific T cells producing IL-5 than those producing IFN-y. The converse was true if the intrapedtoneal route of immunization was used, 36. .
37.
ZHANGZJ, DAVIDXZIN L, EISENBARTN G, WEINERHL: Suppression
of Diabetes in Nonobese Diabetic Mice by Oral Administration of Porcine Insulin. Proc Nat1 Acad Sci USA 1991, S&10252-10256. 38.
..
Responses by the Release of Transforming Growth Factor p after Antigen-specific Triggering. Proc Nat1 Acad Sci USA 1992, 89421-425.
The data reported here provide compelling aidence that TGF-@ plays an important part in the induction of tolerance to an orally administered autoantigen. 39. ..
SEDERRA, BOULAYJ, FINKELMAN F, BARBIER S, BEN-‘&SON SZ, LE GROS G, PAULWE: CD8+ T Cells can be Primed In Vitro
to Produce IL-4 J Immunol 1992, 148:1652-1656. Confirmation that CDS+ T cells can be induced to synthesize IL-4 when activated in the presence of exogenous IL-4. 40.
QIN Y, SUN D, WEKERLF H: Immune Regulation in Self Tolerance: Functional Elimination of a Self-reactive, Counterregulatory CD8+ T Lymphocyte Circuit by Neonatal Transfer of Encephalitogenic CD4+ T Cells Lines. Eur J Immunol 1992, 22:1193-1198.
41.
MATHIESON PW, STAPLETONKJ, OLIVEIRA DB, LOCKWOODCM: Immunoregukion of Mercuric Chloride-induced Autoimmunity in Brown Norway Rats: a Role for CDS+ T Cells Revealed by in Vivo Depletion Studies. Eur J Immunoll991, 21:21052109.
MILLER A, IIDER0, ROBERTS AB, SPORNMB, WEINERHL: Sup-
pressor T Cells Generated by Oral Tolerization to Myelin Basic Protein Suppress both In Vitro and In Vivo Immune
D Mason and D Fowefl, MRC Cellular Immunology Dunn School of Pathology, Oxford OX1 3R!& UK.
Unit, Sir William
subsets in autoimmunity
Don Mason and Deborah Fowell MRC Cellular Immunology
Unit,
The demonstration
Sir William
that functionally
Dunn
different
by the isoforms of the leukocyte-common has prompted have
the ability
shown that diabetes
to inhibit
may
play
system
a role
too,
mediate
in the
it appears
of autoaggressive is evidence
CD45, that they express,
that
autoimmune enterotoxin
pathogenesis
that
subset of CD4+
disease.
this protection
Further,
suggesting
of this
that
disease.
experimental
in Immunology
Introduction Mechanisms mediating self tolerance
The issue of whether self tolerance depends entirely on the mechanisms of clonal deletion and T-cell anergy remains controversial. Although the existence of these mechanisms have been amply demonstrated, they fail to account for all experimental data on autoimmunity. If non-reactivity to self is entirely a consequence of an absence of self-reactive T cells then perturbation of the immune system, for example by neonatal thymectomy or adult thymectomy plus y-irradiation, should not lead to the development of autoimmune disease- but it does in a variety of experimental systems (reviewed in [1,2**] ). These findings have led to the conclusion that normal healthy individuals, with no evidence of organ-specific autoimmune disease, may possess autoreactive T cells that, for some reason, do not express their autoimmune potential. Studies of the response of different mouse strains to pathogenic organisms have shown that the outcome of an antigenic challenge is heavily dependent on genetic variation in the types of cytokine that are elicited by the pathogen in question. Susceptibility to LeiSwnmzia in Balb/c mice arises because the host makes an inappropriate immune response which suppresses the effective one [3**,4,5*]. The demonstration that cytokines can play such potent immunoregulatory roles in infectious diseases has naturally raised the question as to whether similar mechanisms may be involved in regulating autoimmune reactions, in this case to the benefit of the individual [ 2**], In experimental systems, where manipulation of the immune system results in the development of autoimmu-
superantigens in this
the induction diseases there
and that these cells may
by the synthesis of transforming
Opinion
it has been
However,
autoimmune
T cells can be protective
The T cells
by in vitro activation
a subset of T cells can inhibit
cells. In other CD8+
Current
of a particular
in the B-B rat can be transferred
of T cells by Staphylococcal
growth
factor-p.
1992, 4:728732
n&y, the manipulation always produces a degree of immunodeficiency. This fact has led to the proposal of two mechanisms for the breaking of self tolerance. Firstly, environmental antigens, normally eliminated by a competent immune system, can activate in the immunocompromized animal low affinity autoreactive T cells which then upregulate their adhesion molecules and thereby become autoaggressive [6]. These T cells are believed to escape intrathymic clonal deletion by virtue of their low alhnity. Secondly, the immune system possesses T cells that recognize self antigen and these T cells suppress other T cells with autoreactive potential. Note that the protective T cells, although possibly specific for the autoantigen, must be qualitatively different from those that cause disease. Evidence for the second of these two mechanisms can be found in earlier literature. For example, antibody to complement component C5 can be elicited in CS-deficient, but not CS-sufficient, congenic mice and T cells from the CS-sufficient animals can transfer resistance to autoantibody induction [7]. The suppressive T cells were apparently CD8+. Similarly, prostatitis (inflammation of the prostate gland), which developed spontaneously in mice thymectomized on day 3 after birth, was inhibited by a tenfold lower dose of T cells from normal syngeneic male mice than from female mice [8]. A recent paper supports the concept that autoreactivity may be prevented by immunoregulatory T cells that themselves recognize self antigen [S] In these experiments a CD4+ T-cell line, obtained from mice hyperimmunized with testicular germ cells and propagated in vitro by stimulation with mouse testicular antigen in the presence of cyclosporin A, was shown to inhibit the induction of experimental autoimmune orchitis (inflammation of the testis). Both cellular and humoral responses to the
Abbreviations IF&inteferon; 728
IL-interleukin;
UK
T-cell subsets can be defined
antigen,
studies on the roles of these subsets in autoimmunity.
results have led to the identification that
School of Pathology, Oxford,
TGF-transforming
growth factor; Th-T
@ Current Biology Ltd ISSN 0952-7915
helper.
T-cell subsets in autoimmunity
autoantigen were inhibited but the authors did not report on the cytokines produced by the protective cell line. It is evident that the two proposed explanations for the appearance of autoimmunity in relatively immunodeficient animals are not mutually exclusive. In principle, a deficiency of ‘suppressor’ cells could allow activation of low affinity clones to occur at the site of autoantigen expression. In this context , it has recently been reported that Staphylococcal enterotoxin activated spleen cells can passively transfer diabetes in the B-B rat but only if RT6+ CD4+ T cells, which previous studies have implicated in the prevention of diabetes in this rat strain, are excluded from the in vitro culture to which the superantigens are added [lo**]. This result, which resembles a previous one in which Con A was used in vitro to activate the T cells, will be discussed in more detail later in this review.
Subsets of CD4+
T cells
The classical division of lymphocytes derived from the thymus into CD4+ and CD8+ subsets is no longer an adequate indication of the heterogeneity of these cells. In man, mouse and rat, T cells, in particular CD4+ cells, have been shown to be heterogeneous with regard to the cytokines that they synthesize as clones [11*,12,13] and the isoforms of CD45 that they express when freshly isolated from donor animals [ 14.1 (for review see [ I5**]). These facts have led to an extensive study of the properties of these diierent subsets and, although these studies are far from complete, there is clear evidence that there is an association between the CD45 phenotype of a CD4+ T-cell subset before it is activated and the repertoire of cytokines that it secretes on activation [ 16*,17,18]. However, there is not a simple relationship between the type of T helper (Th) cell and CD45 isoform expression and it seems likely that the ThI celVTh2 cell dichotomy represents a terminal state of T-cell specialization [ 19.,20*]. In addition, given the number of known CD45 isoforms, there may be many more unique T-cell phenotypes than are currently identified. The recognition that CD4+ T cells are not functionally homogeneous has resulted in studies of the roles of their subsets in autoimmunity. The data, discussed below, indicate that a subpopulation of T cells with autoimmune potential exists but that these cells are controlled by a different subset of CD4+ T cells. These cells may provide their protective function by inhibiting T-cell activation by superantigens.
induce
subsets of CD4+ and prevent
T cells in the rat
and Fowell
received CD45RChigh CD4+ T cells developed mononuclear cell infiltrates in lung, liver, stomach and pancreas and a few rats also developed thyroiditis with anti-thyroglobulin antibodies. All of these rats died with a progressive wasting disease. In contrast, rats given the CD45RCIoW CD4+ T-cell subset remained well with no inflammatory cell infiltrates in any organ. More significantly, rats given unfractionated CD4+ T cells also remained well, indicating that the CD45RCkW cells in this inoculum somehow inhibited the pathology induced by the CD45RCh@ subset. Thoracic duct lymphocytes from all of these rats contained a high frequency of activated T cells but there was a notable difference in that recipients of the CD45RC1(lWCD4+ subset had T cells that, on isolation from the thoracic duct, were found to be expressing mRNA for interleukin (IL)-4 whereas recipients of CD45RChigh CD4+ T cells were not. This result is consistent with the known cytokine repertoires of these sub sets [ 171. Given the role of IL-4 in inhibiting cell-mediated immune responses and the demonstration that, in the rat, CD45RChigh CD4+ T cells on activation are more potent producers of interferon (IFN)-), and IL-2 than the corresponding CD45RCIOW subset (for review see [ I5**] >, [ 171, then the results obtained from the nude MS could be interpreted as the inhibition by the CD45RCIow subset of an autoimmune cell-mediated reaction produced by the CD45RChigh cells. In the second series of experiments in rats, autoimmune diabetes was induced in PVG.RTl” rats by adult thymectomy and repeated low dose y-irradiation [ 2**]. Diabetes and ins&is in these thymectomized and irradiated PVG.RTl” animals could be completely inhibited b! the intravenous injection of 5 x 106 CD45RCjoW CD4+ T-cell receptor aj3 + RT6+ Thy-l _ T cells from syn geneic donors. In contrast, cells of the CD45RChigh CD4+ phenotype did not protect against diabetes but caused a wasting disease similar to that seen in nude rats given cells of this type. Unfractionated CD4+ T cells were also protective but only in proportion to the CD45RC% cells in the inoculum. This result, like that with the PVG.RTl< nude rats given CD4+ T cells, showed that the protec tive effect of the CD45RCIoW subset was dominant over the pathological effect of the CD45RChigh one. These studies on diabetic rats are consistent with earlier, though less comprehensive, data showing that CD4+ T cells can prevent diabetes in NOD mice [ 21,22 1 and in B-B rats [23], In the latter case, the protcctivc c,rllq were shown to be RT6 +, as in the present experiments Activation
Different
Mason
of diabetogenic
Staphylococcal
T ceils by
enterotoxin
autoimmunity
Two studies of autoimmunity in rats have illustrated the role of different subsets of CD4+ T cells in the induction and prevention of autoimmunity. In the first of these, congenitally athymic (nude) PVG.RTlc rats were injected with CD4+ T-cell subsets from congenic euthymic donors [l]. The CD4+ cells were fractionated on the basis of the level of cell surface expression of exon C of the gene encoding rat CD45. Rats that
Depletion of RT6 + T cells from the diabetes-resistant subline of the B-B rat can result in the spontaneous devel opment of diabetes [24]. In a recent development of this experimental system it has been shown that splenocytes from diabetes-resistant rats, when activated in zdtm with various Staphylococcal enterotoxins, are able to transfer diabetes into young diabetes-prone recipients [lo**]. Interestingly, the adoptive transfer was successful only if the splenocytes were first depleted of RT6+ T cells by in z+z’o
729
730
Autoimmunity
treatment of the spleen donors with anti-RT6 monoclonal antibody. The authors suggest that RT6+ T cells inhibit the Staphylococcal enterotoxin induced activation of the diabetogenic T cells. This result is reminiscent of the protective effect of RT6+ T cells in vivo in both the B-B and the PVG.RTlu rats, however, whether superantigen plays a diabetogenic role in vivo remains to be determined. There is considerable literature on the effect of diet on the incidence of diabetes in the B-B rat but none is very conclusive. Possibly diet affects the intestinal flora in such a way as to promote or impede the production of bacterial superantigens. In this regard it is notable that the intestinal flora has been implicated in determining the incidence of autoimmune thyroidltis in rats [ 25.1. However, it has been reported that the incidence of diabetes in NOD mice is higher in germ-free animals [ 26,271. Thus, the effects of the environment appear complex especially [ 281. when data in man are also considered
Cytokines,
T-cell
subsets and autoimmunity
There are several recent publications which implicate cy tokines in the induction and prevention of autoimmune diseases. Consonant with the ability of IL-4 to inhibit cellmediated immune responses it has been shown that injection of this cytoklne can accelerate recovery from collagen-induced arthritis in mice [29’]. In addition, the treatment of NOD mice with anti-IFN-y antibody has been shown to protect the recipients from diabetes [30,31]. Given that IL-4 can inhibit the induction of IFN-)I [32,33] the result with the NOD mice is consistent with the observation that the subset of CD4+ T cells that prevents diabetes in the lymphopoenic PVG.RTl” rats is the one that produces IL-~.
Other examples of the inhibition of autoimmunity by CD8+ T cells have been reported. Certain CD4+ T-cell lines, specific for myelin basic protein, can elicit experimental allergic encephalomyelitis in Lewis rats. These arimals develop a single episode of disease and are then refractory to further challenge. This refractory phase appears to depend on CD8+ T cells that are specific for the particular CD4+ T-cell line used in the primary challenge. In a recent paper it is reported that neonatal exposure of Lewis rats to a CD4+ encephalitogenic T-cell line abrogates the development of the refractory phase in these rats when they become adults. The abrogation is specific for the CD4+ T-cell line injected neonatally [40]. The authors conclude that the neonatal exposure renders the rats tolerant to the encephalitogenic line so that immunoregulation, mediated by line-specific CD8+ T cells, no longer occurs. To what extent such an immunoregulatory mechanism is of physiological importance is not clear. Rats and mice depleted of CD8+ T cells do not generally develop autoimmune diseases but there is recent evidence that CD8+ T cells may inhibit autoantibody synthesis induced in BN rats by mercuric chloride treatment [41]. The mode of action is not known. Conclusion The conclusion that self tolerance depends, in part, on active T-cell mediated processes seems well founded. Although there is little understanding at present as to how these protective mechanisms work, there is evidence that certain subsets of T cells prevent autoreactivity, possibly by the secretion of particular lymphokines such as IL-4 or TGF-p. Acknowledgements
There have been a number of studies relating abnormal T-cell subset composition in peripheral blood to human autoimmune disease. In the most recent of these it has been shown that patients with mixed connective tissue disease have an abnormally high proportion of CD4+ T cells of the CD45RA+ phenotype [34]. This result resembles that found in an earlier study of insulindependent diabetes where a similar imbalance was reported [35]. The functional significance of these findings remains to be determined.
CD8+
T cells that prevent
autoimmunity
The observation that oral administration of antigen primes Peyer’s patch T cells for a Th2-cell type response [36-I with a high level of IL-5 (and presumably IL-4) production may provide an explanation for the recent demonstration that feeding NOD mice porcine insulin delays the onset and reduces the incidence of diabetes [37]. However, there is evidence that the inhibition of autoimmunity induced by oral tolerance is mediated by transforming growth factor (TGF)-fi produced by CD8+ T cells [38**]. It has also been shown recently that CD8+ T cells can produce IL-4 on appropriate stimulation [39*-l but whether this observation is relevant to oral tolerance is not known.
It is a pleasure
to acknowledge past and present members of the Cellular Immunology Unit that have contributed to these studies, in particular, Andrew McKnight, Fiona Powrie, Neil Barclay and Steve Simmonds.
References
and recommended
reading
Papers review, . ..
of particular interest, published have been highlighted as: of special interest of outstanding interest
within
the annual
period
of
I.
POWRIE F, MASON DW: ox-22high CD4+ T Cells Induce Wasting Disease with Multiple Organ Pathology: Prevention by the OX-22tow Subset. J Eq Med 1!990, 172:1701-1708.
2. ..
FOWELLD, MCKNICH~ AJ, POWRIE F, DVKE R, MASONDW: Subsets of CD4+ T Cells and their Roles in the Induction and Prevention of Autoimmunity. Immunol Rev 1991, 123376% The detailed characterization of the CD4+ T~ceII subset that, on isolation from healthy donors, prevents the development of cell-mediated autoimmune disease. Cells of this phenotype provided secondary B-cell help and on activation produced IL-4. 3. ..
UXKSIEY FCM,HEINZEL FP, HOLADAYBJ, MUTHA SS, RHNER SI., SADICKMD: Induction of Thl and Th2 CD4+ Subsets during
Murine Leishmania Major Infection. Res Immunol 1991, 142:28-32. A valuable review of the roles of IL-4, IFN-y and tumor necrosis factor-a in determining the outcome of Leisbmania infection in different mouse strains.
T-cell
4.
SCOT P: Host and Parasite Factors Regulating the Development of CD4+ T-cell Subsets in Experimental Cutaneous Leishmaniasis. Res Immunol 1991, 142:32-36.
subsets
in autoimmunity
Repertoire of Subsets 1991, 21:1187-1194.
T Cells.
and Fowell
Eur J Immunol
5. .
LFE WT, YIN XM, VITE-ITAES: Functional and Ontogenetic Analysis of Murine CD45Rhi and CD45Rlo CD4+ T Cells. J Immunol 1990, 144:328%3295.
6.
MOSMANNTR: Cytokine Secretion Phenotypes of TH Cells: Res Immunol How Many Subsets, How Much Regulation? 1991, 142:‘+13. An update on the classification of CD4 + T~cell clones into Thl~ and ThZ-cell types indicating that intermediate types also exist.
a Th2 CHATEWN R, VARKI!.AK, COFFMAN RL: IL-4 Induces Response in Leishmania Major-infected Mice. J Immunol 1992, 148:1182-1187. A clear in viva demonstration of the ability of IL-4 injected into mice to inhibit a cell-mediated immune reaction, whilst failing to establish a stable ThZ-cell response in a Thl~type responder mouse strain. SIEGEL KM, KATSUMATA M, KOMOR~ S,
WADSWORTHS, GILL-M•RSI; I., JERROID-JONESS, BHANI~LA A, GREENE MI, Y~JI K: Mechanisms of Autoimmunity in the Context of T-cell Tolerance: Insights from Natural and Transgenic Animal Model Systems. Immunol Rev 1990, 118:165-192.
7.
CAIRNSI., ROSEN FS, BORELy: Mice Naturally Tolerant to C5 have T Cells that Suppress the Response to this Antigen. Eur J Immunol 1986, 16:1277-1282.
8.
TAGUCHI 0, NISH~ZUKA Y: Self Tolerance and Localized Immunity. Mouse Models of Autoimmune Disease that Suggest Tissue-specific Suppressor T Cells are Involved in Self Tolerance. J Exp Med 1987, 165:146156.
9.
ITOH M, MUKASAA, TOKIINAGAY, 111~4~1~~ C, HOJO K: Suppression of Efferent Limb of Testicular Autoimmune Response by a Regulatory CD4+ T CeU Line in Mice. Clin Exp Immunol 1992, 87:455460.
10 ..
K.E, IJKE AA: Staphylococcal Enterotoxin-activated Spleen Cells Passively Transfer Diabetes in BB/Wor Rat. Diabetes 1992, 411527-532. Reports that ubiquitous superantigens may play a role in the activation of autoimmune T cells in diabetes. Also a useful source of references on superantigens.
DEL PRETE G~F,
DE
CARU
M,
MA~TROMAIJRO C,
BL&K)TII
R,
D, FALAG~ANIP, RICCI M, R~MAGNANI S: Purified Protein Derivative of Mycobacterium Tuberculosis and Excretory-Secretory Antigen(s) of Toxocura Canis Expand In Vitro Human T Cells with Stable and Opposite (Type 1 T Helper or Type 2 T Helper) Profile of Cytokine Production. J Clin Invest 1991, 88:346350. MACCHIA
13.
19. .
ANDEFSWN J, ANDERSSOX II: Assessment of Cytokines by Immunofluorescence and the Paraformaldehydesaponin Procedure. Immunol Ret’ 1991, 119:6>93. An elegant study of cytokme synthesis of uncloned human T cells show ing, for example, simultaneous synthesis of IL-4 and IFN-y by a smgle cell
20. .
SANDER B,
21
Hutchings PR, Cooke A: The Transfer of Autoimmune Diabetes in NOD Mice can be Inhibited or Accelerated hy Distinct CeU Populations Present in Normal Splenocytes Taken from Young Males. ,I Autoimmun 1990, 3:175P185.
22.
BOITARD C, Y.~_SINAMI
25.
MOSMANNTR, COFFMANRL: Thl and Th2 Cells: Different Patterns of Lymphokine Secretion Lead to Different Functional Properties. Ann Rev Immunol 1989, 7:14>173.
24.
MA.SOND: Subsets of CD4+ T Cells Defined by their Expression of Diierent Isoforms of the Leukocyte-common Antigen, CD45. Biocbem Sot Transactions 1992, 20:18%190. A concise account of the expression of various CD45 isoforms by CD4+ T cells of the human, mou.se and rat, and how this expression changes with maturation, differentiation and activation. EAR AN, SALMON M, IVORY K, TAKI S, PILLING D, JANOSSY G: Human CD4+CD45RO+ and CD4+CD45RA+ T Cells Synergize in Response to Alloantigens. Eur J Immunol1991, 21~2517-2522. The demonstration that on activation in vitro CD4+ CD45RA+ T cells produce IL-2 only but that CD4+ CD45RO+ cells have a wider cytokine repertoire, consistent with them being previously primed in oivo. MCKNIGHT AJ, BARCLAYAN, MACON DW: Molecular Cloning of Rat Interleukin 4 cDNA and Analysis of the Cytokine
“1.
DL, MOR~ESJP. HANDLEKES, ANGELILLOM. N&%%MI n4 N, ROSSINIAA: Depletion of RT6.1+ T Lymphocytes Induces Diabetes in Resistant Biobreeding/Worcester (RR/W) Rats. .I Eq Med 1987, 166:461475. PENHALE WJ,
YOTING PR: The Influence of the Normal Microbial Flora on the Susceptibility of Rats to Experimental Autoimmune Thyroiditis. Clin Exp fmmrw/ol 1988. 7228x-292. A report that rats reared in specific pathogen free conditions have :I low incidence of experimental allergic thyroiditis but convert to high incidence when exposed to the intestinal flora of rats reared in nclnspecific pathogen free conditions.
26.
WICKER
IS,
MILLER BJ,
COKEK
IZ,
MCNALLY
SE.
SLOTI
5,
MIII~~ Y, AIJI%L MC: Genetic Control of Diabetes and Insulitis in the Non-obese Diabetic Mouse. ./ lhp .Med 19X’. 165:163%1654. 27.
T, FUJIMLVA T, K4whw~4 E. SHI~UZI M R, NOMO’I’OK: Diabetogenic Effects of Lymphocyte Transfusion on the NOD or NOD Nude Mouse. In Immune- deficient Animals in Biochemical Resrurcb. Edited by Rygaard J, Dnmner N, Groem N, Spang~Thomsen M Basel: Karger; 1987:112-116. SUZUKI T,
YAMADA
YAMASHITA
28
Tonn JA: A Protective Role of the Environment in the Development of Type 1 Diabetes? Diabrtic .Ihd 1991. 8:90&910.
~WCEXI~I*I’ JF, I OfiARA J, K_41’% DH. Collagen-induced Arthritis in Mice. Relationship of Collagen-specific and Total IglSynthesis to Disease. J Immunof 1991, 147:41854191 Evidence is presented that the administration of IL~t ian dc,celerare ru covery from an experimental, cell-mediated, autoimmune disease. 29. .
30.
DEBRAY-SACI~S M,
C.~RNAUD C,
BOITARD C,
COHEN
H,
GIU’SSFR
JF: Prevention of Diabetes in NOD Mice Treated with Antibody to Murine IFN Gamma. I Autommun 1991, 4~237-248. 1, BELX%SA P, BACI~
16. .
17.
ES, GREINER DL. NhhAhlw\
GKEINER
25. .
.
15. ..
GAI.I.INA DL, 114~~1~~
MORDF.SJP,
Transfusions Enriched for W3/25 + Helper/Inducer T Lymphocytes Prevents Spontaneous Diabetes in the BBNli Rat. Diabetologia 1987, 3O:Z&26.
14.
WINGA J, GROEN H, KIATTER F, MEEDENDOWB, ASPINALL R, ROSER B, NIEWENHUISP: Postthymic T CeU Development in Rats: an Update. Biocbem Sot Transactions 1992, 20:191-197. Transplantation of primary vascularized thymuses in the rat have ens abled the detailed phenotyping of CD4+ T cells as they leave the thymus and during maturation in the periphery. In the rat, CD4+ cells that have recently migrated from the thymus are CD45RClow Thy-l+ RT6 and mature into peripheral (naive) CD45RC”gh Thy-l RT6+ T cells.
R, DARDI:UYFM, BACH JF, T CeU-mediated Inhibition of the Transfer of Autoimmune Diabetes in NOD Mice. J E.xp Med 1989, 169:166~1680.
PELLETIER A, R~SSINI AA:
EUEw
11. ROMAGNANI S: Human Thl and Th2: Doubt No More. Im. munol Today 1991, 12:256257. A summary of the evidence for functional specialization of human T cells. T~ceU clones with distinct Thl~ or ThZ-cell lymphokine profiles could be isolated from patients with different disease states. 12.
18.
of CD4+
Mason
31.
IL, KAY TW, OXBROW L, H.+wuso~ LC: Essential Role for Interferon-gamma and Interleukin-6 in Autoimmune Insulin-dependent Diabetes in NOD/Wehi Mice. J Clin Invest 1991, 87~739-742.
32.
PELEMANR, Wu J, FARGE.~SC, DELESPFSSEG. Recombinant Interleukin 4 Suppresses the Production of Interferon -/ by Human Mononuclear CeUs. J Exp .Wed 1989, 170:1751-1756.
CAMPBELL
731
732
Autoimmunitv
33.
GEHA RS: IL-4 Inhibits the Synthesis of IFN-y and Induces the Synthesis of IgE in Human Mixed Lymphocyte Cultures. J Immunol 1390, 144:570-573.
VERCELLI D, JABARAHH, IAUENER W,
34.
BECKER H, IANGROCK A, FEDERLIN K: Imbalance of CD4 + Lymphocyte Subsets in Patients with Mixed Connective Tissue Disease. CIin Exp Immunol 1992, 88:91-95.
35.
FAUSTMAN D, E~SENBARTH G, DAIEYJ, BREITMF(ER J: Abnormal
T-lymphocyte 38~1462-1468.
Subsets in Type 1 Diabetes. Diabetes 1989,
Xu-AMANO J, AICHERWK, TAGUCHIT, KXONO H, MCGHEEJR: Selective Induction of Th2 Cells In Murine Peyer’s Patches by Oral Immunisation. Int Immunol 1392, 4:433-445. Mice immunized orally with sheep erythroqtes were found to have a higher frequency of antigen-specific T cells producing IL-5 than those producing IFN-y. The converse was true if the intrapedtoneal route of immunization was used, 36. .
37.
ZHANGZJ, DAVIDXZIN L, EISENBARTN G, WEINERHL: Suppression
of Diabetes in Nonobese Diabetic Mice by Oral Administration of Porcine Insulin. Proc Nat1 Acad Sci USA 1991, S&10252-10256. 38.
..
Responses by the Release of Transforming Growth Factor p after Antigen-specific Triggering. Proc Nat1 Acad Sci USA 1992, 89421-425.
The data reported here provide compelling aidence that TGF-@ plays an important part in the induction of tolerance to an orally administered autoantigen. 39. ..
SEDERRA, BOULAYJ, FINKELMAN F, BARBIER S, BEN-‘&SON SZ, LE GROS G, PAULWE: CD8+ T Cells can be Primed In Vitro
to Produce IL-4 J Immunol 1992, 148:1652-1656. Confirmation that CDS+ T cells can be induced to synthesize IL-4 when activated in the presence of exogenous IL-4. 40.
QIN Y, SUN D, WEKERLF H: Immune Regulation in Self Tolerance: Functional Elimination of a Self-reactive, Counterregulatory CD8+ T Lymphocyte Circuit by Neonatal Transfer of Encephalitogenic CD4+ T Cells Lines. Eur J Immunol 1992, 22:1193-1198.
41.
MATHIESON PW, STAPLETONKJ, OLIVEIRA DB, LOCKWOODCM: Immunoregukion of Mercuric Chloride-induced Autoimmunity in Brown Norway Rats: a Role for CDS+ T Cells Revealed by in Vivo Depletion Studies. Eur J Immunoll991, 21:21052109.
MILLER A, IIDER0, ROBERTS AB, SPORNMB, WEINERHL: Sup-
pressor T Cells Generated by Oral Tolerization to Myelin Basic Protein Suppress both In Vitro and In Vivo Immune
D Mason and D Fowefl, MRC Cellular Immunology Dunn School of Pathology, Oxford OX1 3R!& UK.
Unit, Sir William
