Interleukin-12 administered in vivo decreases human NK cell cytotoxicity and antibody-dependent cellular cytotoxicity to human immunodeficiency virus-infected cells.

Persons infected with human immunodeficiency virus (HIV) have cellular cytotoxicity defects. Interleukin (IL)-12 is a potent stimulator of cytotoxicity. Fifteen HIV-infected patients were studied in a phase 1, single-dose escalation trial of human recombinant IL-12. One day after subjects received an IL-12 dose of 300 or 1000 ng/kg, they had a reduction in absolute lymphocyte count and peripheral blood mononuclear cell recovery. In evaluable patients 24 h after IL-12 administration, there was a 31% reduction overall in NK cell cytotoxicity (NKC) to HIV-infected cells at all doses and a 52% reduction in antibody-dependent cellular cytotoxicity (ADCC) at doses of 300 and 1000 ng/kg. In vitro incubation of patients' cells with IL-12 (before IL-12 administration) for 24 h increased NKC but had no effect on ADCC. The paradoxic acute reduction in cell number and cytotoxicity in vivo may be due to NK cell trafficking or regulatory cytokine mechanisms not apparent in vitro.