Human leukocytic pyrogen induces release of specific granule contents from human neutrophils

The ability of highly purified human leukocytic pyrogen (LP) to induce neutrophil lysosomal protein release is described. Human peripheral blood neutrophils isolated by Ficoll-Hypaque and dextran sedimentation were exposed to purified human LP. The specific granule-associated proteins, lysozyme and lactoferrin were selectively released, whereas primary granule (beta-glucuronidase) and cytoplasmic (lactic dehydrogenase) enzyme markers were not. Optimum release was observed after 45 min in the presence of Ca++ and Mg++. Cytochalasin B (5 microgram/ml) had no effect on LP-induced lysosomal enzyme release. Since the pyrogenicity of LP is dependent on prostaglandin synthesis, the effect of two potent inhibitors of prostaglandin synthesis on lysozyme release was studied. Both indomethacin and naproxen failed to inhibit specific granule protein release. These observations suggest that the concommitance of fever, elevated serum or urine lysozyme and hypoferremia may, in part, be explained by the interaction of LP and peripheral blood neutrophils.