Transforming growth factor‐β2 down‐regulates HLA‐DR antigen expression on human malignant glioma cells.

Abstract

Transforming growth factor-β (TGF-β) is known to have a potent inhibitory influence on several immune functions. It has recently been demonstrated that TGF-β2 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-β2. An optimal concentration of 1 ng/ml TGF-β2 produced a partial but significant decrease of HLA-DR (class II) 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 β2-microglobulin, was not influenced by TGF-β2. The suppressive effect of TGF-β2 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)-γ to the culture system. However, TGF-β2 inhibited the enhancement of HLA-DR surface expression produced by low concentrations of IFN-γ on some cells which initially did not express these antigens. These results show that TGF-β2 can act as a regulator of HLA-DR antigen expression on human glioma cells.