Inducible expression of H–2 and Ia antigens on brain cells

Abstract

Cells in the brain express unusually low levels of antigens encoded by the major histocompatibility complex (MHC). This is somewhat surprising as class I (H-2) and class II (Ia) MHC antigens have critical roles in immune responses. The activation of T lymphocytes is associated with the enhanced expression of these antigens and this effect is mediated by a specific T-cell lymphokine, gamma-interferon (IFN-gamma). Here we show that IFN-gamma induces a dramatic increase in the expression of H-2 antigens on the cells of the brain. After exposure to IFN-gamma in vitro, all surviving cells, including most astrocytes, oligodendrocytes, microglia and at least some neurones, express H-2 antigens. Direct injection of IFN-gamma into the brains of mice indicated that H-2 antigens were also induced in vivo. Furthermore, IFN-gamma induced Ia antigens on a subpopulation of astrocytes. The induction of H-2 antigens by IFN-gamma may render brain cells competent to initiate and participate in immune reactions and may therefore contribute to both immunoprotective and immunopathological responses in the brain.