Clear suppression of Th1 responses but marginal amelioration of autoimmune manifestations by IL-12p40 transgene in MRL-FAS(lprcg)/FAS(lprcg) mice.

To investigate the effects of overproduction of IL-12p40, a potent antagonist against IL-12, on lupus-like autoimmune disease in vivo, we generated p40 transgenic MRL-Fas(lprcg)/Fas(lprcg) mice. Serum p40 and IL-12 levels were 600- to 8000-fold and 3- to 20-fold higher in transgenic (p40-lpr(cg)) than nontransgenic (lpr(cg)) mice, respectively. Serum IFN-gamma levels increased after 3 months of age in lpr(cg) and this age-related increase was completely abrogated in p40-lpr(cg). Serum IL-4 levels were the same in both mice. Production of IgM and IgG anti-double-stranded DNA (dsDNA) antibodies was significantly lower in p40-lpr(cg). Anti-dsDNA antibodies decreased in Th1-dependent IgG2a but increased in the Th2-dependent IgG1 subclass significantly in p40-lpr(cg). Proteinuria, glomerulonephritis, and survival were only marginally ameliorated in p40-lpr(cg). The results suggest that excess p40 production in vivo may suppress Th1 responses in autoantibody and IFN-gamma production but lead to minimal improvement of clinical manifestations of autoimmune disease in this mouse model.