INTERLEUKIN-10 (IL-10) SECRETION IN SYSTEMIC LUPUS-ERYTHEMATOSUS AND RHEUMATOID-ARTHRITIS - IL-10-DEPENDENT CD4-CELL B-CELL ANTIBODY-SYNTHESIS(CD45RO+ T)

Interleukin-10 (IL-10) is a major immunoregulatory cytokine and has a multitude of immunomodulatory effects in the immune system. In this st udy, we have examined the secretion and in vitro function of IL-10 in B cell hyperactivity in antibody production in two common autoimmune d iseases, systemic lupus erythematosus (SLE) and rheumatoid arthritis ( RA). IL-10 was detectable in serum of all active SLE and serum and syn ovial fluid samples of all RA patients but in none of the normal contr ols. B cells and CD4+CD45RO+ ''memory'' T cells secreted highly enhanc ed levels of IL-10 in SLE and RA versus normals. Increased IgM and IgG production by B cells-CD4+CD45RO+ T cells in SLE and RA was IL-10 dep endent, since neutralization of IL-10 cytokine by anti-IL-10 antibody drastically reduced Ig synthesis in these coculture experiments. B cel l hyperactivity in autoantibody production in SLE and RA may be a func tion of IL-10-dependent CD4+CD45RO+ Th2 cell activation. Therefore, IL -10 may play an important role in highly disturbed immune system and B cell-T cell function in these immune disorders.