DIFFERENTIAL INDUCTION OF STRESS PROTEINS AND FUNCTIONAL-EFFECTS OF HEAT-SHOCK IN HUMAN PHAGOCYTES

Induction of specific heat shock (HS) proteins (HSP) has been describe d as a response of human monocytes to phagocytosis, and HSP may play p rotective roles in infection and immunity. Here we compared the stress response in monocytes and polymorphonuclear neutrophils during exposu re to the classical inducers of HSP, i.e., HS and cadmium. We also inv estigated the stress response in these two phagocytic cells after part iculate (phagocytosis) and nonparticulate [f-Met-Leu-Phe (FMLP)] activ ation of the respiratory burst enzyme NADPH oxidase. HS and cadmium in duced stress protein synthesis in both cell types. In contrast, phagoc ytosis induced HSP in monocytes only, while FMLP did so in neutrophils only. This differential regulation of stress proteins might relate to physiological and functional differences between monocytes and neutro phils. With respect to functional effects of HS, we examined, in human monocytes and in neutrophils, the effect of HS on NADPH oxidase-media ted O-2(-) generation as well as on phagocytosis, bacterial killing, a nd superoxide dismutase (SOD) activity. In monocytes, as in neutrophil s, NADPH oxidase activity was inhibited by HS, while thermotolerance p revented this inhibition. Phagocytosis and bacterial killing were unal tered by HS. SOD activity transiently increased in monocytes but decre ased in neutrophils upon exposure to HS. These observations indicate d ifferential induction of HSP in human phagocytes and differential regu lation of phagocytes' functions by HS.