The
interleukin (IL)-12 receptor (R)beta2 subunit is the critical molecule involved in maintaining
IL-12 responsiveness and controlling T helper cell type 1 lineage commitment. We demonstrate that
IL-12 and
interferon (IFN)-gamma play separate, but complementary, roles in regulating IL-12Rbeta2 expression on
antigen-specific CD4(+) T cells. These results are consistent with our previous observation that
IL-12 can promote
autoimmune disease through IFN-gamma-independent as well as -dependent pathways. Therefore, we compared the induction of
IL-12 by, and the expression of the IL-12Rbeta2 subunit on,
myelin basic protein (MBP)-specific T cells from
experimental allergic encephalomyelitis (EAE)-susceptible SJL (H-2(s)) mice and from EAE- resistant B10.S mice (H-2(s)). B10.S mice had an
antigen-specific defect in their capacity to upregulate the IL-12Rbeta2 subunit. Defective expression was not secondary to the production of suppressive
cytokines, but to a failure of B10.S MBP-specific T cells to upregulate
CD40 ligand expression and to induce the production of
IL-12. IL-12Rbeta2 expression as well as encephalitogenicity of these cells could be restored by the addition of
IL-12. These results suggest that the development of
immunotherapies that target the IL-12Rbeta2 subunit may be useful for the treatment of
autoimmune diseases.