CD4+ and CD8+ cells accumulate in the brains of acquired immunodeficiency syndrome patients with human immunodeficiency virus encephalitis.

To test the hypothesis that CD4+ T lymphocytes accumulate in brains of end-stage acquired immunodeficiency syndrome (AIDS) patients, we examined T-lymphocyte subsets in the CA1, CA3, and CA4 regions of the hippocampus of AIDS patients with (n = 10) and without (n = 11) human immunodeficiency virus encephalitis (HIVE) plus controls (n = 7). HIV p24 antigen was common in monocytic cells and rare in activated/memory CD45RO+ lymphocytes. Hippocampal activated/memory CD45RO+ T lymphocytes significantly increased (P <.001) in seven of the eight hippocampal subregions with hippocampal HIVE (1.14 +/- 1.4 T cells/high-power field [hpf]), but AIDS hippocampus without HIVE were similar to controls (0.03 +/- 0.07 T cells/hpf and 0.03 +/- 0.09 T cells/hpf, respectively). CD45RO+ and CD3+ lymphocytes were similar in numbers and distribution, whereas CD4+ and CD8+ lymphocytes were weakly immunoreactive and less frequent. All four lymphocyte subtypes were present in perivascular spaces and microglial nodules of HIVE, and had direct contact with neurons. Monocytes, microglia, and multinucleated giant cells were immunoreactive for CD4 in AIDS cases with hippocampal HIVE but microglia in remaining AIDS cases and controls were CD4-. CD68+ macrophages significantly increased in hippocampus of HIVE patients (P <.05) and were predominately perivascular in the absence of local HIVE. These studies show that CD4+ T lymphocytes, as well as CD8+ T lymphocytes, participate in the local inflammatory response of HIVE in end-stage AIDS patients, and suggest that their recruitment requires local HIV infection. The perineuronal location of CD4+ cells provides the potential for lymphocyte-mediated neuronal injury or trans-receptor-mediated neuronal infection.