Cytokine Secretion by Multiple Sclerosis
Monocytes
Relationship to Disease Activity Richard A. Rudick, MD, Richard M. Ransohoff, MD
Autoantigen recognition by specific T cells may initiate a tissue-specific immune response in multiple sclerosis (MS), which is a chronic inflammatory demyelinating disorder. During subsequent nonspecific immune amplification, interleukin 1\g=b\and tumor necrosis factor \g=a\are released by cells of the monocyte/macrophage lineage, with the potential to influence profoundly immune regulation systemically or within the central nervous system. Regulation of monocyte inflammatory gene expression may be relevant to the pathogenesis of MS. We investigated spontaneous secretion of interleukin 1 \g=b\,tumor necrosis factor a, and prostaglan\s=b\
din E2 with the use of monocytes that we isolated from patients with active (n=9) and stable (n=9) MS and from age-matched normal controls (n = 9). The patient groups with MS were matched for age, duration of MS, and disease severity. Patients with active disease were within weeks of the onset of a clinical exacerbation. Monocytes were isolated by density gradient centrifugation, followed by adherence to plastic tissue culture flasks, resulting in a highly purified adherent monocyte preparation. Monocytes from patients with active disease spontaneously secreted less tumor necrosis factor \g=a\ and less prostaglandin E2 compared with that in patients with stable MS, while interleukin 1\g=b\ levels were below the level of assay sensitivity. Levels of interleukin 1 \g=b\and tumor necrosis factor \g=a\increased to similar levels in response to lipopolysaccharide (0.1 mg/L), indicating that altered cell viability could not account for the observed differences. In response to lipopolysaccharide, prostaglandin E2 levels increased more significantly in patients with stable than active MS, suggesting differential sensitivity to stimuli of arachidonic acid metabolism. The results documented functional differences between monocytes that were isolated from patients with active compared with stable MS and suggested that peripheral inflammatory monokine secretion parallels MS disease activity. (Arch Neurol. 1992;49:265-270)
Accepted
for publication August 21, 1991. From the Department of Neurology, Mellen Center for Multiple Sclerosis Treatment and Research (Drs Rudick and Ransohoff) and Departments of General Medical Sciences (Dr Rudick) and Molec-
(Dr Ransohoff), Cleveland (Ohio) Clinic Foundation. to Mellen Center for Multiple Sclerosis Treatment and Research, Cleveland Clinic Foundation, Cleveland, OH 44195 (Dr Rudick). ular
Biology
Reprint requests
lines of evidence suggest that inflammation in sclerosis (MS) lesion is triggered by spe¬
Severalmultiple the
cific immune
recognition. Circulating lymphoid cells, primarily lymphocytes and monocytes, appear to reg¬
ulate intrathecal inflammation in MS,1 a conclusion that is supported by the therapeutic effects of immunosuppressive regimens targeted to these mononuclear cell popula¬ tions.2 Immune-initiated inflammatory responses require complex intercellular communication, mediated in large part by the secretory products of participating cell popu¬ lations. Products responsible for governing cellular inter¬ actions during inflammation belong to a class of multi¬ functional secreted polypeptides, collectively termed
cytokines. After antigen binding, activated lymphocytes pro¬ duce a first wave of cytokines, such as interleukin 2, in¬ terleukin 4, and interferon gamma (IFN- ). Monocytes elaborate a second wave of cytokines in large quantities, in response to lymphocyte-derived cytokines.3-4 These monocyte products, including tumor necrosis factor ct (TNF-a) and interleukin Iß (IL-lß) exert significant immunoregulatory effects on circulating cells, including lymphocytes, providing signals that may either amplify or inhibit subsequent immunologie events. Additional prod¬ ucts of stimulated monocytes, such as prostaglandins and leukotrienes, also affect the activation
state of immuno-
competent cells. This highly complex interaction of over¬ lapping regulatory influences, including synergy, antag¬ onism, and feedback (both positive and negative), has
been designated the "cytokine network." There is evidence that cytokine secretion by mononu¬ clear cells may vary in concert with MS disease activity. In particular, Beck et al5 performed a longitudinal evalu¬ ation of 20 patients with MS during both active and sta¬ ble phases of disease and detected a significant relation between exacerbations and changes in mitogen-drive production of IFN- and TNF-a by peripheral blood leu¬ kocytes. Dore-Duffy and coworkers6 performed longitu¬ dinal studies of monocyte prostaglandin production in five patients with MS, and they documented markedly reduced prostaglandin release at the onset of exacerbation with subsequent return to preexacerbation levels. Crosssectional comparisons of cytokine and prostaglandin production by leukocytes from groups of patients with MS in active and stable stages of disease have been per-
Downloaded From: http://archneur.jamanetwork.com/ by a University of Arizona Health Sciences Library User on 06/08/2015
formed
and
by Dore-Duffy
colleagues7 and
Merrill and
coworkers,8-9 among others. The results of these investi¬
gations have broadly confirmed the findings from longi¬ tudinal studies, by demonstrating aberrant cytokine and prostaglandin production, which, in some cases, was re¬ lated to disease activity.
This observed linkage between cytokine production and disease activity supports the notion that systemic immunoregulatory events may be integral to formation of the demyelinating lesion. The availability of recombinant cytokines in an unrestricted amount and purity has altered therapy for several neoplastic and viral disorders, indicating the feasibility of using these potent mediators as therapeutic agents in immunopathologic conditions. Further characterization of cytokine and prostaglandin production as a function of MS disease activity will be a required prelude to therapeutic manipulation of circulat¬ ing cytokines in patients with MS. We evaluated cytokine and prostaglandin production by highly purified preparations of monocytes that were isolated from normal controls or patients with MS during periods of stable or active disease. Secreted products were
quantitated by a highly
sensitive
enzyme-linked
immu¬
that exogenous activators were not required to stimulate cytokine synthesis to de¬ tectable levels. We found significant differences between patients in the active and stable groups, by using this as¬ say of spontaneous cytokine production.
nosorbent assay
(ELISA),
so
cells were found to be adherent. Media were free of endotoxin Limulus amebocyte lysate assay (sensitivity,
Monocytes
Relationship to Disease Activity Richard A. Rudick, MD, Richard M. Ransohoff, MD
Autoantigen recognition by specific T cells may initiate a tissue-specific immune response in multiple sclerosis (MS), which is a chronic inflammatory demyelinating disorder. During subsequent nonspecific immune amplification, interleukin 1\g=b\and tumor necrosis factor \g=a\are released by cells of the monocyte/macrophage lineage, with the potential to influence profoundly immune regulation systemically or within the central nervous system. Regulation of monocyte inflammatory gene expression may be relevant to the pathogenesis of MS. We investigated spontaneous secretion of interleukin 1 \g=b\,tumor necrosis factor a, and prostaglan\s=b\
din E2 with the use of monocytes that we isolated from patients with active (n=9) and stable (n=9) MS and from age-matched normal controls (n = 9). The patient groups with MS were matched for age, duration of MS, and disease severity. Patients with active disease were within weeks of the onset of a clinical exacerbation. Monocytes were isolated by density gradient centrifugation, followed by adherence to plastic tissue culture flasks, resulting in a highly purified adherent monocyte preparation. Monocytes from patients with active disease spontaneously secreted less tumor necrosis factor \g=a\ and less prostaglandin E2 compared with that in patients with stable MS, while interleukin 1\g=b\ levels were below the level of assay sensitivity. Levels of interleukin 1 \g=b\and tumor necrosis factor \g=a\increased to similar levels in response to lipopolysaccharide (0.1 mg/L), indicating that altered cell viability could not account for the observed differences. In response to lipopolysaccharide, prostaglandin E2 levels increased more significantly in patients with stable than active MS, suggesting differential sensitivity to stimuli of arachidonic acid metabolism. The results documented functional differences between monocytes that were isolated from patients with active compared with stable MS and suggested that peripheral inflammatory monokine secretion parallels MS disease activity. (Arch Neurol. 1992;49:265-270)
Accepted
for publication August 21, 1991. From the Department of Neurology, Mellen Center for Multiple Sclerosis Treatment and Research (Drs Rudick and Ransohoff) and Departments of General Medical Sciences (Dr Rudick) and Molec-
(Dr Ransohoff), Cleveland (Ohio) Clinic Foundation. to Mellen Center for Multiple Sclerosis Treatment and Research, Cleveland Clinic Foundation, Cleveland, OH 44195 (Dr Rudick). ular
Biology
Reprint requests
lines of evidence suggest that inflammation in sclerosis (MS) lesion is triggered by spe¬
Severalmultiple the
cific immune
recognition. Circulating lymphoid cells, primarily lymphocytes and monocytes, appear to reg¬
ulate intrathecal inflammation in MS,1 a conclusion that is supported by the therapeutic effects of immunosuppressive regimens targeted to these mononuclear cell popula¬ tions.2 Immune-initiated inflammatory responses require complex intercellular communication, mediated in large part by the secretory products of participating cell popu¬ lations. Products responsible for governing cellular inter¬ actions during inflammation belong to a class of multi¬ functional secreted polypeptides, collectively termed
cytokines. After antigen binding, activated lymphocytes pro¬ duce a first wave of cytokines, such as interleukin 2, in¬ terleukin 4, and interferon gamma (IFN- ). Monocytes elaborate a second wave of cytokines in large quantities, in response to lymphocyte-derived cytokines.3-4 These monocyte products, including tumor necrosis factor ct (TNF-a) and interleukin Iß (IL-lß) exert significant immunoregulatory effects on circulating cells, including lymphocytes, providing signals that may either amplify or inhibit subsequent immunologie events. Additional prod¬ ucts of stimulated monocytes, such as prostaglandins and leukotrienes, also affect the activation
state of immuno-
competent cells. This highly complex interaction of over¬ lapping regulatory influences, including synergy, antag¬ onism, and feedback (both positive and negative), has
been designated the "cytokine network." There is evidence that cytokine secretion by mononu¬ clear cells may vary in concert with MS disease activity. In particular, Beck et al5 performed a longitudinal evalu¬ ation of 20 patients with MS during both active and sta¬ ble phases of disease and detected a significant relation between exacerbations and changes in mitogen-drive production of IFN- and TNF-a by peripheral blood leu¬ kocytes. Dore-Duffy and coworkers6 performed longitu¬ dinal studies of monocyte prostaglandin production in five patients with MS, and they documented markedly reduced prostaglandin release at the onset of exacerbation with subsequent return to preexacerbation levels. Crosssectional comparisons of cytokine and prostaglandin production by leukocytes from groups of patients with MS in active and stable stages of disease have been per-
Downloaded From: http://archneur.jamanetwork.com/ by a University of Arizona Health Sciences Library User on 06/08/2015
formed
and
by Dore-Duffy
colleagues7 and
Merrill and
coworkers,8-9 among others. The results of these investi¬
gations have broadly confirmed the findings from longi¬ tudinal studies, by demonstrating aberrant cytokine and prostaglandin production, which, in some cases, was re¬ lated to disease activity.
This observed linkage between cytokine production and disease activity supports the notion that systemic immunoregulatory events may be integral to formation of the demyelinating lesion. The availability of recombinant cytokines in an unrestricted amount and purity has altered therapy for several neoplastic and viral disorders, indicating the feasibility of using these potent mediators as therapeutic agents in immunopathologic conditions. Further characterization of cytokine and prostaglandin production as a function of MS disease activity will be a required prelude to therapeutic manipulation of circulat¬ ing cytokines in patients with MS. We evaluated cytokine and prostaglandin production by highly purified preparations of monocytes that were isolated from normal controls or patients with MS during periods of stable or active disease. Secreted products were
quantitated by a highly
sensitive
enzyme-linked
immu¬
that exogenous activators were not required to stimulate cytokine synthesis to de¬ tectable levels. We found significant differences between patients in the active and stable groups, by using this as¬ say of spontaneous cytokine production.
nosorbent assay
(ELISA),
so
cells were found to be adherent. Media were free of endotoxin Limulus amebocyte lysate assay (sensitivity,
