Loss of encephalitogenicity of a myelin basic protein-specific T cell line is associated with a phenotypic change but not with alteration in production of interleukin-2, gamma-interferon or tumour necrosis factor

Interleukin-1 receptor antagonist suppresses experimental autoimmune encephalomyelitis (EAE) in rats by influencing the activation and proliferation of encephalitogenic cells

Considering the role of pleiotropic interleukin-1 (IL-1) in inflammation and autoimmunity, studies were designed to examine whether specific blockade of IL-1 may influence these processes in the CNS. Although the role of CD4+ T cells in eliciting clinical signs of experimental autoimmune encephalomyelitis (EAE) has been unequivocally demonstrated, the exact mechanism by which encephalitogenic cells initiate disease process and bring about clinical signs still remains to be defined. We have evaluated the effect of human recombinant interleukin-1 receptor antagonist (IL-1Ra) in vivo on the course of actively induced EAE in highly susceptible Dark Agouti (DA) rats. The rats which were treated during the induction phase of disease (days 0-6) with IL-1Ra (350 microg/rat/day) developed milder signs of EAE, when compared to saline-treated control animals immunized with encephalitogen, which developed severe single episode disease. The transfer of lymph node cells (LNC) isolated from MBP-primed DA rats and stimulated in vitro with MBP and ConA to naive syngeneic animals resulted in the development of EAE in all recipients. However, rats injected with LNC that have been stimulated in vitro in the presence of IL-1Ra (10 microg/ml) developed significantly milder disease. Diminished encephalitogenic capacity of LNC correlated with lower proliferative response to antigen and mitogen and decreased expression of IL-2 receptors. These data provide further evidence that IL-1 is an important factor for activation of EAE inducing T lymphocytes.

Tumour necrosis factor and lymphotoxin: molecular aspects and role in tissue-specific autoimmunity

Tumour necrosis factor (TNF) is a highly potent, proinflammatory cytokine with broad-ranging functions from the regulation of endothelial cell adhesion molecules to facilitate entry of leucocytes into tissues, to direct induction of cellular cytotoxicity. This diversity of function potentially attributable to TNF in the genesis of inflammatory disorders place TNF as a primary candidate for clinical targeting and considerable success in this regard has been achieved, particularly in rheumatoid arthritis (RA). In this article we provide a short overview of TNF and its homologue lymphotoxin (LT) alpha and beta. Particular emphasis is placed on recent discoveries regarding the cell surface expression of these cytokines and the role of TNF/LT in experimental autoimmune encephalomyelitis (EAE), an animal model of the human demyelinating disease, multiple sclerosis (MS).

Expression of interleukin-1 beta, interleukin-6 and tumour necrosis factor alpha by macrophages in canine lymph nodes with mineral-associated lymphadenopathy, granulomatous lymphadenitis or reactive hyperplasia

The distribution of CD3+ T lymphocytes and the expression of interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF alpha) by macrophages in canine lymph nodes with mineral-associated lymph-adenopathy, granulomatous lymphadenitis or reactive hyperplasia was examined immunohistochemically. In areas of preserved lymph node architecture, CD3+ T lymphocytes were located in the paracortex, with scattered cells in the follicular mantle and germinal centre, and small aggregates in the medullary cords. T cells were prominent within areas of diffuse granulomatous inflammation and formed a peripheral rim around microgranulomas. TNF alpha expression was demonstrated in macrophages from seven of 11 dogs with mineral-associated lymphadenopathy, one of five dogs with granulomatous lymphadenitis and three of five with reactive hyperplasia. Positive macrophage staining for IL-1 beta and IL-6 was seen in two lymph nodes with reactive hyperplasia. Lymph nodes from control (clinically normal) dogs showed no evidence of cytokine expression. Neutrophils expressing IL-1 beta were observed within the medullary sinuses of two lymph nodes with mineral-associated lymphadenopathy and one with reactive hyperplasia, and in the inflammatory infiltrate in one lymph node with granulomatous lymph-adenitis. The sensitivity of immunohistochemical examination as a means of detecting cytokines in abnormal tissue is discussed.

Tolerogenic forms of auto-antigens and cytokines in the induction of resistance to experimental allergic encephalomyelitis

Resistance to experimental allergic encephalomyelitis (EAE) induction by homogenized myelin (MSCH) in complete Freund's adjuvant (CFA) and pertussigen (P) in SJL mice was seen 1 week after intravenous injection of PLP 139-151 coupled to spleen cells (PLP-ECDI-SP). Although this resistance could be transferred by spleen cells enriched for CD8+ T cells and thus had a component of immunoregulatory T cells, it was primarily due to anergy, as it was reversible by four daily injections of interleukin (II)-2 starting 3 days after the PLP-ECDI-SP. Earlier treatment with IL-2 did not reverse the tolerance. In view of the known higher sensitivity to anergy induction of Th1 than of Th2 cells, a change in the cytokine balance in the response to MSCH+CFA after anergy induction might be responsible for the resistance to EAE induction. The effect of treatment with cytokines alone on induction of EAE was therefore also determined. Short-term (1-2 weeks) daily pretreatment with IL-2 (4000 U) or TGF-beta 2 (1 micrograms) somewhat decreased the susceptibility to subsequent EAE induction, but IL-4 (5 ng), IL-10 (5 micrograms) or IL-12 (50-200 ng) had no effect under those conditions, even if low doses of PLP were injected simultaneously. Daily injections of IL-4 over an 8-week period prior to immunization, however, significantly lowered the incidence of EAE. Simultaneous injections of IFN-gamma (2000 U/day) completely abolished this effect of IL-4. The effect of these cytokines administered immediately after the immunization with MSCH + CFA + P was also examined. As shown earlier, TGF-beta 2 (100-1000 ng/day) caused a marked protection when it was given intraperitoneally on days 5-9 after injection of MSCH + CFA. IL-4 (5 ng/day), in contrast, was very protective when administered on days 0-4 and less so when given on days 5-9 or even on days 0-12. IL-10 (1 microgram/day) was not protective under these conditions and IL-12 (50 ng/day) significantly increased the severity and mortality of EAE when given on days 0-4 after MSCH + CFA.

Control of established experimental allergic encephalomyelitis by inhibition of tumor necrosis factor (TNF) activity within the central nervous system using monoclonal antibodies and TNF receptor-immunoglobulin fusion proteins

Tumor necrosis factor (TNF) activity was inhibited during the development of actively-induced, chronic relapsing experimental allergic encephalomyelitis (CREAE) in Biozzi AB/H mice, using a mouse TNF-specific (TN3.19.12) antibody and bivalent human p55 and p75 TNF receptor-immunoglobulin (TNFR-Ig) fusion proteins. The development of disease could be inhibited when repeated doses of antibody were administered prior to the anticipated onset. It has now also been shown that a therapeutic effect is evident even when antibody is administered after the onset of clinical signs, further indicating an important role for TNF in pathogenic effector mechanisms in CREAE. Although biologically-active TNF was not detected in the circulation, TNF-alpha was detected in lesions within the central nervous system (CNS). This suggested that the CNS may be the main site for TNF-specific immunomodulation and was supported by the observation that intracranial injection was significantly more potent than that administered systemically, for both antibody and TNFR-Ig fusion proteins. The fusion proteins were as effective as antibody at doses 10-100-fold lower than that used for antibody, reflecting their higher neutralizing capacity in vitro. Although treatment was not curative and relapse inevitably occurred in this model if treatment was not sustained, the data indicate that anti-TNF immunotherapy, especially within the CNS, can inhibit CREAE and may, therefore, be useful in the control of human neuroimmunological diseases.

Circulating CD3+ CD4+ CD8+ T lymphocytes in multiple sclerosis

Triple-antibody flow cytometry was used to search for distinctive populations of peripheral blood lymphocyte immunophenotypes in multiple sclerosis (MS). Using monoclonal antibodies to the cell surface markers CD3, CD4, and CD8, T cell subsets were quantified on a cohort of 31 MS patients (not treated with corticosteroids for at least 6 months), 30 healthy donors, and 14 patients with other autoimmune diseases (also corticosteroid treatment-free for at least 6 months). Untreated MS patients displayed a significantly greater population of CD3+CD4+CD8+ circulating T cells than healthy donors (P = 0.023). Patients with other autoimmune diseases displayed mean populations of CD3+CD4+CD8+ cells greater than normal donors and less than MS, but not significantly different from either. An additional 45 MS patients who had received corticosteroid therapy within the previous 6 months were phenotyped. Treatment of symptomatic MS with corticosteroids was associated with a smaller population of circulating CD3+CD4+CD8+ cells. Some MS patients have significantly greater numbers of peripheral blood T lymphocytes simultaneously expressing CD3, CD4, and CD8 surface markers than healthy donors and this population of cells may be reduced by corticosteroids treatment. This triple positive phenotype may be a manifestation of a systemic immune abnormality in MS.

Interleukin-3 and encephalitogenic activity of SJL/J myelin basic protein-specific T cell lines

Myelin basic protein (MBP)-specific SJL/J T cells were cultured in normal growth medium or growth medium supplemented with 10% culture supernatant from WEHI-3 cells, a source of interleukin-3 (IL-3), or with recombinant IL-3. T cell lines cultured with IL-3 supplementation were more encephalitogenic compared to parallel lines cultured without this supplement. There was little difference in antigen-specific proliferative response or expression of cell surface markers CD3, CD4, CD8, IL-2R, or alpha/beta TCR in the parallel lines. Supernatant fluids from antigen-stimulated T cells from each cycle were tested for the presence of IL-2, IL-3, IL-4, granulocyte macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor-alpha (TNF alpha/beta) and transforming growth factor-beta (TGF beta). No significant difference in IL-2, IL-4, GM-CSF, TNF alpha/beta, or TGF beta levels were seen when supplemented and unsupplemented cultures were compared. Supernatant culture fluids contained an activity that was highly stimulatory for the IL-3-dependent mouse mast cell line, MC/9. This activity was attributable to a combination of at least three factors that varied in relative concentrations throughout the course of the experiments. Based on neutralization by monoclonal antibodies, MC/9 stimulating activity in early passage lines was attributable entirely to IL-3 and GM-CSF. The fraction of the MC/9 stimulatory activity that could be neutralized by monoclonal antibody to IL-3 decreased with increasing stimulation cycle while the fraction neutralized by anti-GM-CSF antibodies remained relatively constant. At the time that the lines lost encephalitogenicity, the activity neutralizable by anti-IL-3 had dropped to low levels in the culture supernatants; however, MC/9 stimulatory activity remained present in the supernatants. This was due to GM-CSF and a third unidentified factor.

Expression of CD45RC and Ia antigen in the spinal cord in acute experimental allergic encephalomyelitis: an immunocytochemical and flow cytometric study

We performed immunocytochemical studies to analyze the inflammatory infiltrate and major histocompatibility complex class II (Ia) antigen expression in the spinal cord of Lewis rats with acute experimental allergic encephalomyelitis (EAE) induced by inoculation with myelin basic protein and adjuvants. Using antibodies to lymphocyte markers and other monoclonal antibodies we found that during clinical episodes the inflammatory infiltrate was chiefly composed of T lymphocytes and macrophages. The majority of cells in the inflammatory infiltrate were stained by the W3/25 antibody to CD4 and a proportion was stained by OX22 which labels the high molecular weight form of the leucocyte common antigen (CD45RC). CD8+ T cells were sparse and B cells were not detected. There was minimal staining with the OX39 antibody to the interleukin-2 receptor. Presumptive microglia, identified by their dendritic morphology, expressed Ia antigen during the clinical episodes and after recovery. The prominence of Ia antigen expression after recovery could indicate that this Ia expression was associated with downregulation of the encephalitogenic immune response. We also performed flow cytometry studies on cells extracted from the spinal cord of rats before and during attacks of EAE. With flow cytometry, we found that in established disease a mean of 83(SD, 23)% of CD2+ cells were CD4+, and a mean of 27(SD, 12)% of CD2+ cells were CD45RC+. In rats sampled on the first day of signs, a mean of 43(SD, 22)% of CD2+ cells were CD45RC+. In the cells extracted from the spinal cord of rats with established disease a mean of 47(SD, 32)% of macrophages were CD45RC+. Our study has combined an immunocytochemical assessment of tissue sections with quantitative flow cytometry assessment of cells extracted from the spinal cord of rats with acute EAE. We have shown that the majority of T lymphocytes in the spinal cord are CD45RC-. We have also found prominent Ia expression on dendritic cells in acute EAE and after clinical recovery.