We have derived a panel of CD4+, TCR-alpha/beta + T cell clones from SJL (H-2s) mice specific for an encephalitogenic determinant of myelin proteolipid protein (PLP) 139-151 (HSLGKWLGHPDKF). All the clones are Ag specific and IAs restricted, but they show heterogeneity in their ability to induce experimental allergic encephalomyelitis (EAE), i.e., one group induces EAE in naive mice, a second group induces disease only in mice that are pretreated with pertussis and irradiation, whereas a third group is essentially nonencephalitogenic. To determine the basis for this functional heterogeneity, the clones were tested for the expression of adhesion molecules and cytokines and for Ag-specific cytolytic activity. All of the clones expressed comparable levels of LFA-1 and CD44 but lacked expression of Mel 14. However, those clones that induced EAE only in irradiation- and pertussis-treated recipients did not express VLA4. Because pretreatment with pertussis has been suggested to increase permeability of the blood-brain barrier and facilitate migration of T cells into the central nervous system, the absence of VLA4 on this group of clones may account for the need for pretreatment to induce EAE. The nonencephalitogenic clones expressed all of the adhesion molecules tested but were not cytolytic in vitro and failed to produce one or more of the proinflammatory cytokines after Ag-specific stimulation. One nonencephalitogenic clone that did not produce many cytokines on activation with specific Ag, however, could be activated with Con A to express mRNA for most cytokines and this was accompanied by a concomitant change in the encephalitogenic potency of this clone. These results suggest that adhesion molecules and cytokines both play a critical role in the encephalitogenicity of PLP peptide-specific T cell clones. Furthermore, the nonencephalitogenicity of some clones may be related to a defect in Ag-mediated activation.

Previously, six T cell clones, which are specific for an encephalitogenic determinant of myelin proteolipid protein (PLP) peptide residues 139 to 151 (HSLGKWLGHPDKF), were derived from SJL mice and shown to use diverse TCR genes. To design TCR antagonist peptides that could interfere with the activation of these clones in vitro and inhibit experimental allergic encephalomyelitis (EAE) in vivo, we first determined the TCR and MHC contact residues of the encephalitogenic peptide. The analysis indicated that residues 144 (tryptophan) and 147 (histidine) were the TCR binding sites and that residues 145 (leucine) and 148 (proline) were important for MHC class II (IAs) binding. On the basis of this information, a peptide analogue (leucine 144/arginine 147), in which both of the major TCR contact residues were substituted, was synthesized. This analogue acts as a TCR antagonist for the panel of PLP 139-151-specific T cell clones, does not cause EAE by itself, blocks the induction of disease by the native 139-151 peptide, and prevents clinical disease progression if administered at the first signs of disease. Thus, although multiple TCR genes are used by PLP 139-151-specific clones, a single peptide analogue can interfere with the disease process. This approach should be feasible for designing peptide analogues that can be tested for therapeutic efficacy in human autoimmune diseases in which the pathogenic Ags are known and TCR use is diverse.

Background: There is reported to be a decline in immune function and an alteration in the frequency of circulating lymphocytes with advancing age. There are also differences in ageing and lifespan between males and females. We performed this study to see if there were differences between males and females in the frequency of the different lymphocyte subsets with age.Results: Using flow cytometry we have examined different populations of peripheral blood leukocytes purified from healthy subjects with age ranging from the third to the tenth decade. We used linear regression analysis to determine if there is a linear relationship between age and cell frequencies. For the whole group, we find that with age there is a significant decline in the percentage of naïve T cells and CD8⁺T cells, and an increase in the percentage of effector memory cells, CD4⁺foxp3⁺T cells and NK cells. For all cells where there was an effect of ageing, the slope of the curve was greater for men than for women and this was statistically significant for CD8⁺αβ⁺T cells and CD3⁺CD45RA^-CCR7^-effector memory cells. There was also a difference for naïve cells but this was not significant.Conclusion: The cause of the change in percentage of lymphocyte subsets with age, and the different effects on males and females is not fully understood but warrants further study.

We briefly survey the concept of autoimmunity and nominate the range of autoimmune diseases that include multisystemic and organ-specific disorders, and cite prevalences of autoimmune diseases in males and females, in humans and in experimental animals. Most human autoimmune diseases such as systemic lupus erythematosus (SLE), multiple sclerosis (MS) and autoimmune thyroid disease, have an increased incidence and prevalence in females, but a few others such as autoimmune diabetes, the Guillain Barre syndrome (GBS) and psoriasis are increased in males. Animal models of autoimmunity show an equivalent sexual dimorphism. The possible reasons for the differing incidence and prevalence of autoimmune diseases in females and males engage our attention. Environmental exposures may differ for females and males. There are innate differences in the function of the female and male immune systems, and there is some evidence for differences between females and males in the ability of a target organ for autoimmunity to withstand damage. In seeking reasons for these differences, we review the role of sex hormones in immunity and include results of trials of hormone therapy in autoimmune diseases. The association of autoimmunity and pregnancy, a female-specific condition, is discussed, and the claimed effects of lymphoid cell microchimerism on provocation of autoimmunity are reviewed. Genetic predisposition is an important factor in autoimmune disease and we particularly focus on genes on the X and Y chromosomes, the role of X chromosome inactivation, and the interaction of the sex of the patient with other genetic factors. The possible role of epigenetic mechanisms, including environmental influences, is then surveyed. We assert that sex is a vital variable that must be considered in all immunological studies, as it should be at all levels of biological research.