Immunology Today, voL 4, No. 11, 1983
310 aspects of reproductive failure were aH fully discussed. Within the specialized meeting there was much opportunity also to apply updated concepts of immunoregulation and other basic aspects of immunology to considerations of the successful maternal acceptance of the fetal allograft in pregnancy. The first congress was opened by C. Polge (Babraham, UK) who graphically illustrated veterinary examples of in-vitro fertilization techniques and the viable interspecies chimeras that can now be produced (e.g. sheep/goat). These rather bizarre situations give food for thought on the nature of fetal antigen presentation in pregnancy as well as the control of host maternal antigen processing in utero. The full list of known natural and artificial chimeric situations, which is surprisingly long, was scientifically reviewed by R. Billingham (Dallas) who concentrated particularly on aspects of reproductive immunology analogous to chimerism transplantation biology: materno-fetal cellular traffic and the transfer of viable cells from the mother to offspring in breast milk. The possible consequences of exaggerated cellular transfer was stressed - - the establishment of chimerism, maternally induced tolerance and graft-vs-host disease. It is reassuring that recent FACS analyses and studies on glucose phosphate isomerase isoenzymes suggest that in general only a small number of cells are transferred from mother to fetus (T. Wegmann, Edmonton), although the very occasional fetus may be severely compromised by transfer of allogeneic maternal cells or primed lymphoid cells reactive with fetal alloantigens. Extensive immunological investigations have been done on M u s caroli/Mus musculus chimeras gestating in Mus musculus uteri and other combinations within this system (A. Croy, St. Catherine's, Ontario); this work highlighted the importance not only of relevant antigen expression on fetal trophoblast but also of the recruitment of a suppressor lymphoid cell population to the uterine decidua to prevent effective cytotoxic T-cell responses and subsequent fetal resorption. Indeed, much attention was attracted by studies describing immunocompetent cells (notably of a suppressor phenotype) that infiltrate into uterine decidua in pregnancy. For example, R. Slapsys and D. Clark (Hamilton, Ontario) described a suppressor-cell population (small granulated lymphoid cells lacking mature T-cell markers) which accumulates in the uterus and lymph nodes draining the uterus of allopregnant mice and is potent in blocking the generation ofcytotoxic T cells against
paternal alloantigens. In women in early pregnancy, infiltrating granulated cells of bone marrow origin have been observed by immunohistology on decidual tissues using monoclonal antibodies to lymphoid cellular differentiation antigens (J. Bulmer, Bristol). Presumably these cells, together with the macrophage populations in uterine decidua, locally control the balance and nature of development of maternal responses to fetal antigens. Although more must be discovered about the functional character of different maternal cell types in the pregnant uterus, the working hypothesis now emerging is that specialized lymphoid cells may be attracted into the uterine decidua, perhaps by the release of chemotactic signals from host endometrial cells following decidualization. Questions arise therefore about the nature of the fetal antigen system which may contribute to any initial signal and the type of complex immunoregnlation system that is needed. There is, indeed, substantial extravillous fetal trophoblast invasion into maternal decidua. These cells are now known to express some characteristics trophoblastic surface antigens, and, unlike placental villous trophoblastic cell populations, can be strongly reactive with W6/32 monoclonal antibody (C. Redman, Oxford; B. Hsi, Nice). This reactivity has been assumed to represent the expression of dass-I M H C antigen by extravillous trophoblastic cells but
contrasting results were reported when other monoclonal antibodies to class-I determinants were used, so it is questionable whether W6/32 reactivity in this context represents the detection of H L A A,B,C antigens or perhaps a less polymorphic gene product encoded from the T l a region. There was much active but unresolved discussion around this important point. The reproductive immunology congress strongly reinforced the impression that the techniques of molecular genetics may clarify the nature of M H C antigen expression by fetal trophoblast more rapidly than will the application of monoclonal antibodies. Indeed, soluble products of placental cells impair a variety of cytotoxic systems (G. Chaouat, Vinejuif) and induce suppressor-cell activity (T. Hamaoka, Osaka). But there were intriguing hints in presentations on a diversity of topics that a membrane-associated MHC-linked gene product may be central to local control of suppressor cell and possibly also alloantibody responses to the feto-placental unit. Such allusions were present, for example, in the immunogenetic analyses of reproduction in rats (T. Gill, Pittsburgh) and studies of habitual abortion in women (A. Beer, Ann Arbor). This may be speculative but, to paraphase a Chinese proverb, every journey of a thousand miles begins with a single step. P. M. Johnson is in the Departmentof lmmunolog~, UniversiOpof Liverpool, UK.
Immunoparasitology
Antigens yield to new technology from Derek Wakelin
Immunoparasitology is a vigorous science, drawing from and contributing to many immunological disciplines. This was amply confirmed at Kyoto by the number and variety of presentations in the field and by the footsore immunoparasitologists commuting between the many sessions relevant to their interests. One symposium dealt with the regulation of immune responses to infectious agents and gave a valuable overview of responses to organisms as diverse as influenza virus and Schistosoma mansoni. The present and future impact of hybridoma technology, gene cloning, peptide sequencing and synthesis upon immunoparasitological research was dearly apparent in the reviews on leprosy (B. Bloom, New York), malaria (V. and R. Nus~enzweig, New York) and schistosomiasis (A. Capron, Lille).
Monoclonal antibodies are available for surface antigens of sporozoites of many malarial species and in each, the antigen recognized is a single protein species with many repeated sequences; in V. Nussenzweig's words, the sporozoite is a floating polymer. Peptides from the sporozoite antigens of Hasmodium knowlesi have been synthesized and tested for in-vivo protective activity. Monoclonal antibodies recognizing epitopes common to the tegument of early schistosomula and metabolic products of adult S. mansoni have been developed and used to isolate the molecules concerned. The antigens protect experimental hosts and are recognized by antibodies from infected patients. Is this a molecular basis for concomitant immunity? The tripeptide (Thr-LysPro) cleaved from bound IgGl by
Immunology Today, vol. 4, No. 11, 1983
enzymes released from schistosomes in vitro has been synthesized. It strikingly inhibits macrophage function and may prove a novel immunopharmacological agent. A. Capron emphasized that analysis of lack of protection may be as valuable as the study of immunity. This point was taken up by A. Sher (Bethesda) in the context of parasite genetics. He reviewed work on isolates of Trypanosoma cruzi and Leishmania brasiliensis which differed distinctively from other strains in their responses to effector mechanisms. The former did not react with monoclonal antibodies to a surface glycoprotein of molecular weight 78 000 present in other strains while the latter established chronic infections by failing to stimulate the respiratory burst even in activated macrophages. All the speakers referred to the question of vaccines. R. Arnon (Rehovot) described .the substantial progress made in devising synthetic vaccines against influenza virus, using short peptides to raise antibodies capable of neutralizing the intact virus. Immunity has been raised in vivo with a wholly synthetic antigen-carrier-adjuvant combination - a hopeful pointer for future anti-parasite vaccines. Three workshops dealt specifically with parasite immunity and immunopathology (helminths, malaria and other protozoa, tropical diseases) and one covered parasite antigens. Many other workshops contained immunoparasitological contributions (for example, allergy, eosinophils, gut immunology, immunogenetics). Selection from the many posters and papers is invidious, but many attracted attention. Genes of blood-stage Plasmodium falciparum have been successfully cloned in Escherichia coli and 78 clones established so far (R. Anders, Melbourne). One gene product is identical with an S antigen common to several Papuan isolates of this species. The antigen is structurally homologous to but not identical with sporozoite surface antigen; antibodies to it have no effect on growth in vitro. A 24 amino-acid peptide of P. knowlesi sporozoite antigen has been synthesized and raised some immunity in monkeys (R. Nussenzweig). T ceils capable of transferring immunity to Hasmodium yoelii can be generated in vitro using infected reticulocytes (H-2 K/Dpositive). Mature erythrocytes (MHC class-I-antigen-positive) generated suppressor cells with in-vivo activity (D. Green, New Haven). I. Clark (Canberra) explained the persistence of favism in G6PD-negative populations via a selective advantage in malarious areas. Divicine mediates release of
311 oxygen metabolites which kill parasites in erythrocytes. S. Reed (New York) gave two interesting papers, one analysing deregulation of immunity in visceral leishmaniasis, the other showing that a liposome-carried lymphokine greatly reduced in-vivo burdens after infection. Several aspects of trypanotolerance were presented. M. Pinder (Bobo-Dioulasso, U. Volta) showed that the relative resistance of N'dama cattle does not correlate with antibody responses. Immunosuppression during T. cruzi infection in mice was correlated with failure of lymphocytes to produce or respond to interleukin 2 (IL-2) (A. Harel-Bellarn, Paris). F. Kierzenbaum (E. Lensing, USA) reported that human polymorphs could phagocytose and kill T. cru.zi amastigotes. T-lymphocyte subset inbalances in human schistosomiasis were described by H. Feldmeier (Hamburg). T. Abe (Miyazaki) described an I-J +, anti-idiotypic T-ceil suppressor factor which modulated granuloma formation. Invitro models for studying bladder cancer caused by Schistosoma haematobium have been developed by P. Das (Amsterdam). Immune responses to egg-hatching fluid are an important contributory factor. Platelets are now added to the list of cells involved in antibody-dependent ceilmediated cytotoxicity (ADCC) of schistosomula (C. Auriault, Lille). N. Bianco (Caracas) summarized work on the immunopathology of onchocerciasis which implicated circulating antigen and immune complexes in immune depression and systemic vasculitis. T-cell clones specific for antigens of Trichinella spiralis have been developed by C. Krco (Rochester). They are being used to analyse genetic control of antiparasite responsiveness, in which H-2linked genes play an important role (C. Krco; D. Wakelin, Nottingham). M. Dy (Paris) described the production of a his-
tamine-producing, ceil-stimulating factor by lymphocytes during infection with Nippostrongylus. Since this is similar to interleukin 3 (IL-3), it may be identical with the P-cell stimulating factor described by J. Schrader and I. ClarkLewis (Melbourne) in another workshop, i.e. a T-cell product regulating mastocytosis. T cells migrate into the gut of Giardia-infected mice during the phase of rapid clearance (M. Heyworth, San Francisco). A role for IgA in control of G. mum was deduced by B. Underdown (Toronto) from the chronic nature of infection in IgM-negative, IgA-positive mice. The isolation and characterization of a protein antigen from taeiniid onchospheres was described by M. Rickard (Melbourne). The antigen is protective in vivo. Further data on eosinophilmediated antibody-dependent cytotoXicity against S. mansoni and on IgE receptors on these ceils were given by M. Capron (Lille). Eosinophils clearly fall into several types, characterized by differences in buoyant density, receptor density, granule content and cytotoxic efficiency. P.-C. Tai (London) described anti-eosinophil monoclonal antibodies which may help in subset definition and in unravelling pathology. Eosinophils were shown to phagucytose amastigotes of T. cruz.i(M. Di Prisco-F., Caracas) but eosinophils do have some opposition. Y. Nawa (Kumamoto) described depression of gut eosinophilia mediated by worm-derived factors in Nippostrong~lus infections. The rate of progress reflected by immunoparasitological presentations at Kyoto seems such that one can confidently expect the solution of many outstanding problems by 1986, when we meet again in Toronto. Derek Wakelin is in the Department of Zoology, University of Nottingham, Nottingham NG7 2RD, UK.
Transplantation
Allograft response dissected from John Fabre The rejection of a fully incompatible allograft is immunologically complex at many levels, and is therefore a model system largely and understandably avoided by basic immunologists. However, it is by a careful study of the individual pieces of the complex jigsaw that we can try to build up a working model of graft rejection. Tl'/ere were many interesting and relevant facets of basic ira-
munology discussed at Kyoto, and some :interesting work with real grafts as well. From a practical point of view, I found the most compelling studies were in the area of graft-versus-host disease. J. Sprent (Philadelphia) summarized his very detailed and systematic studies on graft vs host (GVH) disease in the mouse, demonstrating that GVH disease involving minor histocom-
310 aspects of reproductive failure were aH fully discussed. Within the specialized meeting there was much opportunity also to apply updated concepts of immunoregulation and other basic aspects of immunology to considerations of the successful maternal acceptance of the fetal allograft in pregnancy. The first congress was opened by C. Polge (Babraham, UK) who graphically illustrated veterinary examples of in-vitro fertilization techniques and the viable interspecies chimeras that can now be produced (e.g. sheep/goat). These rather bizarre situations give food for thought on the nature of fetal antigen presentation in pregnancy as well as the control of host maternal antigen processing in utero. The full list of known natural and artificial chimeric situations, which is surprisingly long, was scientifically reviewed by R. Billingham (Dallas) who concentrated particularly on aspects of reproductive immunology analogous to chimerism transplantation biology: materno-fetal cellular traffic and the transfer of viable cells from the mother to offspring in breast milk. The possible consequences of exaggerated cellular transfer was stressed - - the establishment of chimerism, maternally induced tolerance and graft-vs-host disease. It is reassuring that recent FACS analyses and studies on glucose phosphate isomerase isoenzymes suggest that in general only a small number of cells are transferred from mother to fetus (T. Wegmann, Edmonton), although the very occasional fetus may be severely compromised by transfer of allogeneic maternal cells or primed lymphoid cells reactive with fetal alloantigens. Extensive immunological investigations have been done on M u s caroli/Mus musculus chimeras gestating in Mus musculus uteri and other combinations within this system (A. Croy, St. Catherine's, Ontario); this work highlighted the importance not only of relevant antigen expression on fetal trophoblast but also of the recruitment of a suppressor lymphoid cell population to the uterine decidua to prevent effective cytotoxic T-cell responses and subsequent fetal resorption. Indeed, much attention was attracted by studies describing immunocompetent cells (notably of a suppressor phenotype) that infiltrate into uterine decidua in pregnancy. For example, R. Slapsys and D. Clark (Hamilton, Ontario) described a suppressor-cell population (small granulated lymphoid cells lacking mature T-cell markers) which accumulates in the uterus and lymph nodes draining the uterus of allopregnant mice and is potent in blocking the generation ofcytotoxic T cells against
paternal alloantigens. In women in early pregnancy, infiltrating granulated cells of bone marrow origin have been observed by immunohistology on decidual tissues using monoclonal antibodies to lymphoid cellular differentiation antigens (J. Bulmer, Bristol). Presumably these cells, together with the macrophage populations in uterine decidua, locally control the balance and nature of development of maternal responses to fetal antigens. Although more must be discovered about the functional character of different maternal cell types in the pregnant uterus, the working hypothesis now emerging is that specialized lymphoid cells may be attracted into the uterine decidua, perhaps by the release of chemotactic signals from host endometrial cells following decidualization. Questions arise therefore about the nature of the fetal antigen system which may contribute to any initial signal and the type of complex immunoregnlation system that is needed. There is, indeed, substantial extravillous fetal trophoblast invasion into maternal decidua. These cells are now known to express some characteristics trophoblastic surface antigens, and, unlike placental villous trophoblastic cell populations, can be strongly reactive with W6/32 monoclonal antibody (C. Redman, Oxford; B. Hsi, Nice). This reactivity has been assumed to represent the expression of dass-I M H C antigen by extravillous trophoblastic cells but
contrasting results were reported when other monoclonal antibodies to class-I determinants were used, so it is questionable whether W6/32 reactivity in this context represents the detection of H L A A,B,C antigens or perhaps a less polymorphic gene product encoded from the T l a region. There was much active but unresolved discussion around this important point. The reproductive immunology congress strongly reinforced the impression that the techniques of molecular genetics may clarify the nature of M H C antigen expression by fetal trophoblast more rapidly than will the application of monoclonal antibodies. Indeed, soluble products of placental cells impair a variety of cytotoxic systems (G. Chaouat, Vinejuif) and induce suppressor-cell activity (T. Hamaoka, Osaka). But there were intriguing hints in presentations on a diversity of topics that a membrane-associated MHC-linked gene product may be central to local control of suppressor cell and possibly also alloantibody responses to the feto-placental unit. Such allusions were present, for example, in the immunogenetic analyses of reproduction in rats (T. Gill, Pittsburgh) and studies of habitual abortion in women (A. Beer, Ann Arbor). This may be speculative but, to paraphase a Chinese proverb, every journey of a thousand miles begins with a single step. P. M. Johnson is in the Departmentof lmmunolog~, UniversiOpof Liverpool, UK.
Immunoparasitology
Antigens yield to new technology from Derek Wakelin
Immunoparasitology is a vigorous science, drawing from and contributing to many immunological disciplines. This was amply confirmed at Kyoto by the number and variety of presentations in the field and by the footsore immunoparasitologists commuting between the many sessions relevant to their interests. One symposium dealt with the regulation of immune responses to infectious agents and gave a valuable overview of responses to organisms as diverse as influenza virus and Schistosoma mansoni. The present and future impact of hybridoma technology, gene cloning, peptide sequencing and synthesis upon immunoparasitological research was dearly apparent in the reviews on leprosy (B. Bloom, New York), malaria (V. and R. Nus~enzweig, New York) and schistosomiasis (A. Capron, Lille).
Monoclonal antibodies are available for surface antigens of sporozoites of many malarial species and in each, the antigen recognized is a single protein species with many repeated sequences; in V. Nussenzweig's words, the sporozoite is a floating polymer. Peptides from the sporozoite antigens of Hasmodium knowlesi have been synthesized and tested for in-vivo protective activity. Monoclonal antibodies recognizing epitopes common to the tegument of early schistosomula and metabolic products of adult S. mansoni have been developed and used to isolate the molecules concerned. The antigens protect experimental hosts and are recognized by antibodies from infected patients. Is this a molecular basis for concomitant immunity? The tripeptide (Thr-LysPro) cleaved from bound IgGl by
Immunology Today, vol. 4, No. 11, 1983
enzymes released from schistosomes in vitro has been synthesized. It strikingly inhibits macrophage function and may prove a novel immunopharmacological agent. A. Capron emphasized that analysis of lack of protection may be as valuable as the study of immunity. This point was taken up by A. Sher (Bethesda) in the context of parasite genetics. He reviewed work on isolates of Trypanosoma cruzi and Leishmania brasiliensis which differed distinctively from other strains in their responses to effector mechanisms. The former did not react with monoclonal antibodies to a surface glycoprotein of molecular weight 78 000 present in other strains while the latter established chronic infections by failing to stimulate the respiratory burst even in activated macrophages. All the speakers referred to the question of vaccines. R. Arnon (Rehovot) described .the substantial progress made in devising synthetic vaccines against influenza virus, using short peptides to raise antibodies capable of neutralizing the intact virus. Immunity has been raised in vivo with a wholly synthetic antigen-carrier-adjuvant combination - a hopeful pointer for future anti-parasite vaccines. Three workshops dealt specifically with parasite immunity and immunopathology (helminths, malaria and other protozoa, tropical diseases) and one covered parasite antigens. Many other workshops contained immunoparasitological contributions (for example, allergy, eosinophils, gut immunology, immunogenetics). Selection from the many posters and papers is invidious, but many attracted attention. Genes of blood-stage Plasmodium falciparum have been successfully cloned in Escherichia coli and 78 clones established so far (R. Anders, Melbourne). One gene product is identical with an S antigen common to several Papuan isolates of this species. The antigen is structurally homologous to but not identical with sporozoite surface antigen; antibodies to it have no effect on growth in vitro. A 24 amino-acid peptide of P. knowlesi sporozoite antigen has been synthesized and raised some immunity in monkeys (R. Nussenzweig). T ceils capable of transferring immunity to Hasmodium yoelii can be generated in vitro using infected reticulocytes (H-2 K/Dpositive). Mature erythrocytes (MHC class-I-antigen-positive) generated suppressor cells with in-vivo activity (D. Green, New Haven). I. Clark (Canberra) explained the persistence of favism in G6PD-negative populations via a selective advantage in malarious areas. Divicine mediates release of
311 oxygen metabolites which kill parasites in erythrocytes. S. Reed (New York) gave two interesting papers, one analysing deregulation of immunity in visceral leishmaniasis, the other showing that a liposome-carried lymphokine greatly reduced in-vivo burdens after infection. Several aspects of trypanotolerance were presented. M. Pinder (Bobo-Dioulasso, U. Volta) showed that the relative resistance of N'dama cattle does not correlate with antibody responses. Immunosuppression during T. cruzi infection in mice was correlated with failure of lymphocytes to produce or respond to interleukin 2 (IL-2) (A. Harel-Bellarn, Paris). F. Kierzenbaum (E. Lensing, USA) reported that human polymorphs could phagocytose and kill T. cru.zi amastigotes. T-lymphocyte subset inbalances in human schistosomiasis were described by H. Feldmeier (Hamburg). T. Abe (Miyazaki) described an I-J +, anti-idiotypic T-ceil suppressor factor which modulated granuloma formation. Invitro models for studying bladder cancer caused by Schistosoma haematobium have been developed by P. Das (Amsterdam). Immune responses to egg-hatching fluid are an important contributory factor. Platelets are now added to the list of cells involved in antibody-dependent ceilmediated cytotoxicity (ADCC) of schistosomula (C. Auriault, Lille). N. Bianco (Caracas) summarized work on the immunopathology of onchocerciasis which implicated circulating antigen and immune complexes in immune depression and systemic vasculitis. T-cell clones specific for antigens of Trichinella spiralis have been developed by C. Krco (Rochester). They are being used to analyse genetic control of antiparasite responsiveness, in which H-2linked genes play an important role (C. Krco; D. Wakelin, Nottingham). M. Dy (Paris) described the production of a his-
tamine-producing, ceil-stimulating factor by lymphocytes during infection with Nippostrongylus. Since this is similar to interleukin 3 (IL-3), it may be identical with the P-cell stimulating factor described by J. Schrader and I. ClarkLewis (Melbourne) in another workshop, i.e. a T-cell product regulating mastocytosis. T cells migrate into the gut of Giardia-infected mice during the phase of rapid clearance (M. Heyworth, San Francisco). A role for IgA in control of G. mum was deduced by B. Underdown (Toronto) from the chronic nature of infection in IgM-negative, IgA-positive mice. The isolation and characterization of a protein antigen from taeiniid onchospheres was described by M. Rickard (Melbourne). The antigen is protective in vivo. Further data on eosinophilmediated antibody-dependent cytotoXicity against S. mansoni and on IgE receptors on these ceils were given by M. Capron (Lille). Eosinophils clearly fall into several types, characterized by differences in buoyant density, receptor density, granule content and cytotoxic efficiency. P.-C. Tai (London) described anti-eosinophil monoclonal antibodies which may help in subset definition and in unravelling pathology. Eosinophils were shown to phagucytose amastigotes of T. cruz.i(M. Di Prisco-F., Caracas) but eosinophils do have some opposition. Y. Nawa (Kumamoto) described depression of gut eosinophilia mediated by worm-derived factors in Nippostrong~lus infections. The rate of progress reflected by immunoparasitological presentations at Kyoto seems such that one can confidently expect the solution of many outstanding problems by 1986, when we meet again in Toronto. Derek Wakelin is in the Department of Zoology, University of Nottingham, Nottingham NG7 2RD, UK.
Transplantation
Allograft response dissected from John Fabre The rejection of a fully incompatible allograft is immunologically complex at many levels, and is therefore a model system largely and understandably avoided by basic immunologists. However, it is by a careful study of the individual pieces of the complex jigsaw that we can try to build up a working model of graft rejection. Tl'/ere were many interesting and relevant facets of basic ira-
munology discussed at Kyoto, and some :interesting work with real grafts as well. From a practical point of view, I found the most compelling studies were in the area of graft-versus-host disease. J. Sprent (Philadelphia) summarized his very detailed and systematic studies on graft vs host (GVH) disease in the mouse, demonstrating that GVH disease involving minor histocom-
