Transforming growth factor-fi2 down-regulates HLA-DR antigen expression on human malignant glioma cells
Transforming growth factor-fl (TGF-P) is known to have a potent inhibitory influence on several immune functions. It has recently been demonstrated that TGF-P2 is identical to the glioblastoma-derived T cell suppressor factor (G-TsF). In the present study, human malignant glioma cell lines were incubated with various concentrations of TGF-P2. An optimal concentration of 1 ng/ml TGF-P2 produced a partial but significant decrease of HLA-DR (class 11) surface antigen expression on glioma cells expressing this antigen, as well as decreased levels of HLA-DR-specific mRNA. The surface expression of other HLA-related molecules, such as HLA-ABC (class I) and Pz-microglobulin, was not influenced by TGF-P2. The suppressive effect of TGF-P2 on HLA-DR expression, both at the surface antigenic and cytoplasmic mRNA levels, could be completely overcome by adding relatively high concentrations (500 U/ml) of interferon (1FN)-y to the culture system. However, TGF-62 inhibited the enhancement of HLA-DR surface expression produced by low concentrations of IFN-y on some cells which initially did not express these antigens. These results show that TGF-p2 can act as a regulator of HLA-DR antigen expression on human glioma cells.