Interleukin 6 (IL-6) is an autocrine growth factor of cultured mesangial cells (MC) and intraglomerular IL-6 production is suggested to be closely associated with the pathogenesis of human mesangial proliferative glomerulonephritis (mesPGN). In this study, to elucidate the mechanisms regulating the intraglomerular production of IL-6, we examined what kinds of stimuli are significant in the induction of IL-6 synthesis in vitro and in vivo. Incubation of cultured mesangial cells with interleukin 1 (IL-1) or bacterial lipopolysaccharide (LPS) induced significant IL-6 production, and intravenous injection of IL-1 or LPS into normal BALB/c mice induced significant intraglomerular IL-6 mRNA expression. Furthermore, we indicated in this study that IL-6 mRNA expression was augmented in the glomeruli of mice with immune complex-mediated glomerulonephritis.