Glomerular mesangial cells in local inflammation. Induction of the expression of MHC class II antigens by IFN-γ

Glomerular mesangial cells (MC) were isolated from rats and cultured for a prolonged period of time, resulting in a homogenous cell population. MC were characterized as belonging to the smooth muscle type. They were negative for MHC class II expression. IFN-γ and TNFα suppressed the proliferation of MC, demonstrating receptors for these cytokines on MC. IFN-γ or TNFα, respectively, enhanced basal MHC class I Ag expression of proliferating cells in culture. The combination of the two cytokines yielded stronger effects. IL-1β was ineffective in enhancing MHC class I Ag expression, although MC possessed receptors for this cytokine. IFN-γ dose dependently induced the expression of MHC class II Ag, while TNFα or IL-1β were ineffective alone. The combination of IFN-γ with TNFα or IL-1β resulted in an enhanced induction of MHC class II Ag, compared to IFN-γ administration alone. These findings suggest that proliferating mesangial cells of the smooth muscle type may participate in local inflammatory responses or substitute for macrophages by meeting the accessory cell requirement in the interaction with T lymphocytes. Furthermore, the data have important implications for the evaluation of the role of mesangial cells in autoimmune diseases of the kidney.