To determine whether HIV-1-mediated induction of CD95/Fas apoptosis in CD4+ T cells is largely attributed to productive infection or bystander effects of the virus, we cultured purified CD4+ T cells and PBMC from the same healthy donors in parallel with HIV-1 for 72 hours, followed by a 14 hour stimulation with immobilized anti-CD95 antibodies. The gene discussed is FAS; the disease is infection.