Biological response modifier enhances the activity of natural killer cell against human cytomegalovirus-infected cells

Abstract

Peripheral blood lymphocytes (PBL) from two human cytomegalovirus (CMV)‐seronegative donors and eight CMV‐seropositive donors were cultured for 3 days with or without the biological response modifier OK‐432 and examined for lysis of K562 cells and CMV‐infected MRC‐5 cells. OK‐432–stimulated PBL exhibited significantly greater natural killer (NK) activity than did unstimulated PBL. There was no difference in activity of NK cells in PBL prepared from CMV‐seronegative and ‐seropositive donors. Antibody‐complement depletion studies suggested that OK‐432–stimulated NK activity was associated with Leu‐7–positive cells. The ability of OK‐432 to sustain the NK activity in PBL was decreased when the CD4‐positive population of lymphocytes was eliminated by antibody‐complement depletion prior to OK‐432 stimulation. The ability of OK‐432 to sustain the NK activity of PBL was also significantly decreased in the presence of monoclonal antibody against recombinant human interleukin‐2. The results suggest that the activity of human NK cells against K562 and CMV‐infected MRC‐5 target cells can be sustained in vitro by OK‐432‐stimulated T‐helper cells and that the effect of the T‐helper cells is mediated, at least in part, by interleukin‐2.