AIDS - Subacute (giant cell) encephalitis: A perivascular mononuclear cell infiltrate is evident in the left side of this photomicrograph, as are widely scattered reactive astrocytes in the surrounding white matter. This illustrates the inflammatory nature of this disorder and its predominance in white matter. In addition, multinucleate cells, such as the one in mid right of the field, are thought to be infected with HIV and result from fusion of monocytes/macrophages as a result of HIV binding to cell membranes.