GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR INHIBITS CLASS-II MAJOR HISTOCOMPATIBILITY COMPLEX EXPRESSION AND ANTIGEN PRESENTATION BY MICROGLIA

Granulocyte-macrophage colony stimulating factor (GM-CSF) modulates va rious functions of monocytes/macrophages including antigen-presenting capacity. Recently it was found that astrocytes produce GM-CSF in the central nervous system (CNS) and that GM-CSF can induce proliferation and morphological changes of microglia. Here we show that GM-CSF can d own regulate the interferon-gamma-mediated induction of major histocom patibility complex (MHC) class II antigens in microglia, but not in as trocytes. GM-CSF pretreatment completely prevents myelin basic protein -specific T cell proliferation induced by microglia but not astrocytes . GM-CSF did not affect the cell surface expression on microglia of ei ther MHC class I or cell adhesion molecules. The inhibition of microgl ial MHC class II expression and antigen-presenting function is specifi c for GM-CSF, as treatment with a different CSF (interleukin-3) did no t modulate microglial phenotype or functional capacity. These data sug gest that GM-CSF might be involved in the regulation of immune respons es within the central nervous system.