Response of glioma cells to interferon‐gamma: increase in class II RNA, protein and mixed lymphocyte reaction‐stimulating ability

Previous results by ourselves and others demonstrated that brain cells and cell lines express major histocompatibility complex class II antigens. We examined interferongamma (IFN‐γ)‐mediated induction of human class II antigen expression on the glioma cells. Purified IFN‐γ induced the expression of HLA‐DR antigens on the surface of the glioma cell lines U‐373 MG and U‐105 MG. Concomitant increase of HLA‐DR_α‐and HLA‐DC_β‐specific RNA in the cytoplasm was also observed after treatment with IFN‐γ. Increases of class II antigen paralleled the increased level of class II‐specific RNA. The effect of IFN‐γ on the induction of human class II antigen expression was dose and time dependent. A marked induction of human class II antigen expression was observed when glioma cells were cultured with more than 100 U/ml of IFN‐γ. Little or no induction was observed with less than 50 U/ml of IFN‐γ. Compared to human blood monocytes, glioma cells needed higher concentrations of IFN‐γ for the induction of class II antigen expression. In allogenic mixed lymphocyte cultures, the glioma cell line U‐373 MG stimulated a mixed lymphocyte response (MLR). MLR‐stimulating capacity was augmented by IFN‐γ. The concomitant augmentation of class II antigen levels and MLR‐stimulating capacity suggests that the most relevant factor for MLR stimulation may be antigen density. This is the first report of MLR stimulation by a glioma cell line.