Enhancement of T helper2 response in the absence of interleukin (IL-)6; an inhibition of IL-4-mediated T helper2 cell differentiation by IL-6.

Functional roles of interleukin (IL-)6 in T cell response were investigated. Mice deficient in IL-6 and wild mice were immunized with antigens (myelin oligodendrocyte glycoprotein or methylated BSA) and production of IL-4 and interferon (IFN)-gamma by regional lymph nodes was measured. IL-6 deficiency led to an enhancement of IL-4 and an inhibition of IFN-gamma production. Moreover, polyclonal stimulation of spleen T cells from unimmunized IL-6-deficient mice with anti-CD3 plus anti-CD28 antibodies (Abs) demonstrated an enhancement of T helper (Th)(2)responses. The presence of IL-6, however, augmented IL-4 production but it inhibited IFN-gamma expression by spleen T cells in response to polyclonal stimulation and by antigen-primed spleen T cells in response to re-challenge with the antigen. In contrast, the induction of spleen CD4-positive T cells into Th(2)cells in vitro by the anti-CD3 plus IL-4 was completely suppressed by exogenously added IL-6, whereas Th(1)differentiation of T cells by the anti-CD3 plus IL-12 was not inhibited by the presence of IL-6. Thus, these results indicate that IL-6 physiologically could modulate qualitative T cell response and suggest that it augments Th(1)responses partly through its inhibitory capability of IL-4-induced Th(2)differentiation of naive T cells. Copyright 2001 Academic Press.