MHC class II expression by human glioma cells after in vitro incubation with soluble antigens.

Recent studies have suggested that astrocytes share with the macrophages several properties in vitro, among which is the ability to express MHC Class II molecules and to present some antigens to syngeneic primed lymphocytes (MHC-restricted presentation). It has been claimed in the literature that astrocytes cannot start the presentation and cannot express the related MHC Class II molecules if not previously stimulated with gamma IFN. In this paper we report that 2 human GFAP + glioma cell lines, incubated in culture with various soluble antigens for at least 24 h, were able, in the absence of gamma IFN or of activated lymphocytes, to express the MHC Class II and to expose the antigens on their surfaces. Moreover, when a lysosomotropic agent such as chloroquine was added during the incubation, no MHC Class II expression was observed. This last datum suggests that in astrocytes, as is already known in macrophages, the processing of antigens and their assembling with MHC Class II molecules probably involves the lysosomal apparatus.