The differential effects of polymorphonuclear leukocyte secretion on human natural killer cell activity

We studied the differential effects of polymorphonuclear leukocyte (PMN) secretion on human natural killer cells (NK) and lymphokine-activated killer cell (LAK) activity. Supernatant fluids from PMN stimulated by serum-opsonized zymosan (SOZ), n-formylmethionylleucylphenylalanine (FMLP) and interleukin-8 (IL-8) were incubated with peripheral blood lymphocytes (PBL) for 1 d and 4 d. Supernates from unstimulated PMN and PMN induced by FMLP and IL-8 decreased NK and LAK cytotoxicity in a dose-dependent fashion against K562 and M14 targets, respectively. Only the suppression caused by supernates from unstimulated PMN was ablated by incubation of PMN with indomethacin. Secretions from PMN stimulated by SOZ increased both NK and LAK cytotoxicity and induced PBL proliferation synergistically with IL-2. This enhancing factor was heat-labile, nondialyzable (MWCO 3500), and not blocked by anti-interferon-gamma. Anaerobic conditions did not influence the modulatory activity of PMN supernates, indicating that oxygen metabolites were not involved. We conclude that PMN release factors that modulate in vitro NK and LAK activities.