Programmed Cell Death Induced by HIV Type 1 Antigen Stimulation Is Associated with a Decrease in Cytotoxic T Lymphocyte Activity in Advanced HIV Type 1 Infection

Abstract

The immune competence of peripheral blood mononuclear cells (PBMCs) from human immunodeficiency virus-seropositive (HIV⁺) patients was studied by assessing cytotoxic T lymphocyte (CTL) activity following recall HIV antigen stimulation. Target cells were HLA-A-matched EBV-transformed B cells expressing HIV-1 antigen. In the presence of recombinant IL-2 (rIL-2,2 or 10 U/ml), about 50% of PBMCs from HIV⁺ asymptomatic patients responded to HIV-1 antigen stimulation in vitro with increased cytotoxic activity. In contrast, PBMCs from patients with overt AIDS, cultured in medium containing rIL-2 (2 U/ml) and HIV-1 antigen, showed no increase in cytotoxic activity; in the presence of rIL-2 (10 U/ml) and HIV-1 antigen, an inhibitory effect on CTL activity was observed. This inhibitory effect was associated with programmed cell death (apoptosis) of CD8⁺ lymphocytes and cells of both γ/δ TcR-positive and -negative phenotypes. However, prior to the apoptosis, different TcR phenotypes of T lymphocyte reacted differently to HIV-1 antigen stimulation. The HIV-1 antigen initially appeared to cause γ/δ TcR-positive T lymphocytes to proliferate and/or differentiate and later induced cell death. Whereas, prior to the apoptosis, no proliferation of γ/δ TcR-negative T lymphocytes induced by HIV-1 antigen was observed.