Immunogenicity and arthritogenicity of recombinant CB10 in B10.RIII mice.

Two major T cell determinants are recognized by I-Ar-specific T cells in CII, the immunodominant CII610-618 (GPAGT AGA R) within CB10 and the subdominant CII445-453 (GPAGP AGE R) within CB8. Although the determinants differ by only two residues, CB8 is capable of inducing collagen-induced arthritis (CIA), while CB10 is not. We, therefore, investigated the structural differences between the two determinants that are critical to inducing arthritis. When the CB10 determinant was mutated to that of CB8 using recombinant techniques, the resulting mutant rCB10T614P,A617E product became arthritogenic. Conversely, when the CB8 determinant was mutated to that of CB10, the resulting mutant CB8P449T,E452A was no longer arthritogenic. Comparison of the epitope specificity of the autoantibodies induced by wild-type CB10 and mutant rCB10T614P, A617E revealed no qualitative differences. T cells from mice immunized with either CB10 or mutant rCB10 produced predominantly Th1 cytokines when cultured with the immunizing Ag. In contrast, when cultured with mouse CII, T cells from mice immunized with the nonarthritogenic CB10 produced predominantly Th2 (IL-4 and IL-10) cytokines whereas the arthritogenic mutant rCB10 induced predominantly Th1 (IFN-gamma) cytokines. We conclude that the T cell cytokine response most critical for the induction of CIA is that induced against the corresponding homologous murine T cell determinant and, further, that the structural differences between the T cell determinants in CB8 and -10 are important in breaking self tolerance and inducing autoimmune response.