[Studies on expression and function of Eta-1(early T lymphocyte activation-1) in autoimmune prone MRL/Mp-lpr/lpr...

The role of CD4-CD8-(double negative; DN) T cells on the polyclonal activation of B cells which might lead to autoantibody production and hyper gamma-globulinemia was studied in autoimmune-prone MRL/Mp-lpr/lpr mice. The expression of various cytokine mRNA in various T cell subsets was examined by using RT-PCR (Reverse Transcriptase-Polymerase Chain Reaction) method. CD4+ T cells as well as DNT cells constitutively expressed IFN-gamma, TNF-alpha, and TNF-beta genes. Importantly IL-3, IL-4, IL-5, or IL-6, which are supposed to stimulate B cell activation and differentiation was not expressed by DNT cells. In contrast, DNT cells constitutively expressed Eta-1 mRNA. Eta-1 was known to be expressed by normal T cells short after the activation and active B cells and macrophages to produce polyclonal Ig production. Therefore, in this study, the role of Eta-1 on polyclonal B cell activation was studied by using highly purified colostrum Eta-1. In addition, I found that Eta-1 titer is elevated in serum of MRL/lpr mice but not of control mice. Taken together, it is conceivable that in MRL/lpr mice Eta-1 is produced by DNT cells in vivo and induce polyclonal activation of B cell loading to hyper gamma-globulinemia and autoantibody production.