Immune modulation within the brain: recruitment of inflammatory cells and increased major histocompatibility antigen expression following intracerebral injection of interferon-gamma.

Intracerebral injections of interferon-gamma (IFN-gamma) have multiple immunological effects on rat brain, affecting all anatomic compartments. Lymphocytes and other inflammatory cells are recruited to the injection site: CD4+ T-cells into the perivascular space, OX42+ monocytes/macrophages into brain parenchyma. IFN-gamma also recruits OX8+ cells into brain parenchyma. These OX8+ cells are not stained by 'pan' T-cell antibodies, however, suggesting that they may be natural killer cells. IFN-gamma also causes increased major histocompatibility complex expression on brain cells: class I antigen on local endothelial and ependymal cells, and class II antigen on microglial, ependymal, and perivascular cells throughout both hemispheres of the brain.