The role of CTLA-4 in tolerance induction and T cell differentiation in experimental autoimmune encephalomyelitis: i.v. antigen administration

Interactions between B7 molecules on antigen-presenting cells and CTLA-4 on T cells have been shown to be important in establishing tolerance. In the present study, we examined the kinetics of tolerance induction following i. v. administration of myelin bas;ic protein (MBP) Ac1-11 in mice transgenic for a TCR V(beta)8.2 gene derived from an encephalitogenic T cell clone spe cific for MBP Ac1-11. Examination of the lymph node cell (LNC) response 10 days after antigen administration demonstrated an accentuation of i.v. tole rance induction with anti-CTLA-4 blockade. Anergy was induced in splenocyte s by i.v. antigen administration as shown by a decrease in MBP-specific pro liferation and IL-2 production, and anti-CTLA-4 potentiated this effect. In addition, i.v. antigen plus anti-CTLA-4 and complete Freund's adjuvant was not encephalitogenic, Interestingly, i.v. tolerance (a single injection) d id not inhibit experimental autoimmune encephalomyelitis (EAE) and anti-CTL A-4 administration did not alter this phenotype, These results suggest that while the majority of MBP-specific T cells are tolerized by i.v. antigen a nd that this process is potentiated by anti-CTLA-4 administration, a popula tion of T cells remains that is quite efficient in mediating EAE.