CULTURED RAT AND PURIFIED HUMAN PNEUMOCYSTIS-CARINII STIMULATE INTRACELLULAR BUT NOT EXTRACELLULAR FREE-RADICAL PRODUCTION IN HUMAN NEUTROPHILS

The production of free radicals in human neutrophils was studied in bo th Pneumocystis carinii derived from cultures of L2 rat lung epithelia l-like cells and Pneumocystis carinii purified from human lung. Using the cytochrome C technique, which selectively measured extracellular s uperoxide generation, hardly any free radical production was observed after stimulation with cultured rat-derived P. carinii. A chemilumines cence technique, which separately measured intra- and extracellular fr ee radical production, was subsequently employed to differentiate the free radical generation. It was established that 1) P. carinii stimula ted intra- but not extracellular free radical production in human neut rophils, 2) opsonized cultured rat-derived P, carinii stimulated human neutrophils to a strong intracellular response of superoxide producti on, and 3) opsonized P, carinii, purified from human lung also stimula ted human neutrophils to produce intracellular free radicals.