Immunocytochemical analysis of the cellular infiltrate in brain lesions in subacute sclerosing panencephalitis.

We studied lymphocyte subsets and major histocompatibility complex (MHC) class II antigens in frozen brain tissues from three patients with subacute sclerosing panencephalitis (SSPE) using immunocytochemical techniques. Perivascular cuffs consisted predominantly of T cells and MHC class II-positive cells. In the parenchymal lesions, there were frequent B and CD4+ cells. MHC class II-positive cells were also diffusely distributed throughout the parenchyma. There were more CD4+ than CD8+ cells both in the parenchyma and in the perivascular cuffs. These findings suggest an overrepresentation of CD4+ cells in SSPE lesions and that CD4+ cells may be involved in the pathogenesis of SSPE.