Patterns of cytokine production in human immunodeficiency virus type 1 (HIV-1)-specific human CD8⁺ T cells after stimulation with HIV-1-infected CD4⁺ T cells

Although human immunodeficiency virus type 1 (HIV-1)-specific CD8 ⁺ T cells can produce various cytokines that suppress HIV-1 replication or modulate anti-HIV-1 immunity, the extent to which HIV-1-specific CD8⁺ T cells produce cytokines when they recognize HIV-1-infected CD4⁺ T cells in vivo still remains unclear. We first analyzed the abilities of 10 cytotoxic T-lymphocyte (CTL) clones specific for three HIV-1 epitopes to produce gamma interferon, macrophage inflammatory protein 1β, and tumor necrosis factor alpha after stimulation with epitope peptide-pulsed cells. These CTL clones produced these cytokines in various combinations within the same specificity and among the different specificities, suggesting a functional heterogeneity of HIV-1-specific effector CD8⁺ T cells in cytokine production. In contrast, the HIV-1-specific CTL clones for the most part produced a single cytokine, without heterogeneity of cytokine production among the clones, after stimulation with HIV-1-infected CD4⁺ T cells. The loss of heterogeneity in cytokine production may be explained by low surface expression of HLA class I-epitope peptide complexes. Freshly isolated HIV-1-specific CD8⁺ T cells with an effector/memory or memory phenotype produced much more of the cytokines than the same epitope-specific CTL clones when stimulated with HIV-1-infecied CD4⁺ T cells. Cytokine production from HIV-1-specific memory/effector and memory CD8⁺ T cells might be a critical event in the eradication of HIV-1 in HIV-1-infected individuals.