T cells and microglia in brains of chronically infected mice. Representative images of one of five infected mice. T lymphocytes were present in nodules and in the perivascular spaces in frontal cortex and diencephalons. CD4 T lymphocytes and microglia and CD8 T lymphocytes ×40. Immunohistochemical stains for CD11 indicate activated microglia. × 100. H & E stains also were performed. In contrast, preparations of brains from 5 uninfected mice revealed no inflammatory cells other than occasional microglial cells (not shown). Secondary antibody control stained tissues had no background staining (not shown).