Suppression of lymphokine-activated killer (LAK) cell function by neutrophil polymorphonuclear leukocytes

Peripheral blood neutrophil polymorphonuclear leukocytes (PMN) from healthy donors were found to inhibit the cytolytic efficiency of interleukin 2 (IL-2)-activated lymphocytes (LAK cells) in a dose-dependent manner. The inhibitory activity of PMN was not merely due to PMN acting as cold alternative targets, PMN ingestion of the label released by target cells or cell overcrowding in test wells. Heat-treated (50 degrees C, 30 min) lysates from PMN maintained their ability to inhibit LAK cell cytotoxicity, whereas PMN supernatants were completely ineffective. Oxidant scavengers (catalase, superoxide, dismutase) did not affect the PMN-mediated inhibition of LAK cell function. The results suggest that PMN contain heat-stable factor(s) able to suppress LAK cytotoxicity and potentially capable of limiting the therapeutic efficacy of IL-2 and/or LAK cells.