Mice having a point mutation of IL-6 signal transducer, gp130, named gp130F759 induced a rheumatoid arthritis-like disease. The disease induction is totally dependent on mature lymphocytes, since no arthritis-like disease induced in a double mutant between gp130F759 and RAG2KO mice. We prepared several other double mutants including gp130F759/IgMKO, gp130F759/CD8KO, gp130F759/CIITAKO and gp130F759/CD4KO and analyzed the development of the arthritis. We found that development of the disease attenuated in gp130F759/CIITAKO and gp130F759/CD4KO, suggesting the MHC class II-restricted CD4+ T cells are important for the disease development. We showed memory/activated phenotype of CD4+ T cells increased in gp130F759 mice. Since activation of CD4+ T cells is mainly controlled by dendritic cells (DC) in vivo, we investigated this feature of DC in gp130F759 mice. We isolated DCs from superficial lymph nodes and observed that IL-6-mediated signaling suppresses maturation of DCs in vivo. However, total number of DCs in vivo significantly increased in gp130F759 mice compared with wild type controls. Thus, we hypothesize that the rheumatoid arthritis-like disease in gp130F759 mice is induced by an interaction between CD4+ T cells and DC under gp130F759 signal regulation.
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