Activation of microglial and endothelial cells in the rat brain after treatment with interferon‐gamma in vivo

Activation of microglial cells occurs during the pathogenesis of various neurologic diseases. However, the mechanisms of activation in vivo are still elusive. We infused adult rats intravenously with interferon‐γ and demonstrated microglial cell activation after three days of treatment. We show for the first time that microglial cells proliferate inside the brain in response to a circulating cytokine. Microglial cells were induced to express major histocompatibility (MHC) class I and class II antigens and small amounts of leukocyte function‐associated molecule 1 (LFA‐1, CD11a). On endothelial cells of the brain, MHC class I and class II antigens and intercellular adhesion molecule 1 (ICAM‐1, CD54) were enhanced. GLIA 19:181–189, 1997. © 1997 Wiley‐Liss, Inc.