Antibody-dependent cellular cytotoxicity mediated by CD16+ lymphocytes from HIV-seropositive homosexual men

We investigated the ability of peripheral blood mononuclear cells (PBMC) from human immunodeficiency virus (HIV)-seropositive asymptomatic and mildly symptomatic homosexual men with known time of seroconversion to mediate antibody-dependent cellular cytotoxicity (ADCC) specific for HIV. PBMC from HIV-seronegative and -sero-positive subjects lysed T (CEM) cells persistently infected with HIV to a significantly greater degree than uninfected CEM cells in the presence of HIV antibody-positive serum in a 4-hr 51Cr release assay. The response was mediated by CD16+ cells. ADCC responses were lower in PBMC of 13 men tested 9 to 25 months (average, 16.1 months) after seroconversion to HIV as compared with seronegative subjects, and were further decreased in 11 men tested 26 to 38 months (average, 31.6 months) after seroconversion. Decreases in numbers of circulating CD16+ cells appeared to contribute to depression in ADCC activity. The suppressive effect of HIV infection on ADCC effector cell activity may be important in the immunopathogenesis of acquired immune deficiency syndrome.