Accumulation of CD8⁺ T lymphocytes in the brain during HIVE. Increased number of CD8⁺ lymphocytes within the neuropil in HIVE brains (A) as compared with the seropositive patients without evidence of encephalitis (insert). Infiltrating CD8⁺ lymphocytes (purple) migrate toward HIV-1⁺ MPs (brown) of microglial nodule (B,C). The inset in panel A shows lymphocytes contained within the perivascular cuff in the HIV⁺ case. Human brain sections were double-immunostained with antibodies to CD8⁺ (purple, VIP substrate) and HIV-1 p24 (brown, DAB substrate). Original magnifications: panels A and B: ×100; panel C: ×200. (D) CD8⁺ lymphocytes were counted in basal ganglia and frontal cortex (white matter) of human brains (average of 10 consecutive 20 × fields). ^*P < .05 compared with HIV-seropositive and -seronegative controls. Error bars indicate standard error of the mean (SEM).