GROWTH-HORMONE AND INSULIN-LIKE-GROWTH-FACTOR-1 AUGMENT BACTERICIDAL CAPACITY OF HUMAN POLYMORPHONUCLEAR NEUTROPHILS

Effects of growth hormone (GH) and insulin-like growth factor (IGF)-I on bactericidal capacity of human polymorphonuclear neutrophils (PMNs) were investigated. Venous blood was collected from healthy volunteers . in Experiment 1, PMNs were isolated, incubated with GH or IGF-I, and cocultured with Escherichia coli. E. coli-killing capacity, viability , and CD11b and CD16 expressions of PMNs were then assessed. Both GH a nd IGF-I enhanced E. coli killing by PMNs. GH preserved PMN viability during E. coli killing, whereas IGF-I enhanced PMN CD11b expression be fore coculture with E, coli, In Experiment 2, whale blood was washed a nd incubated with GH or IGF-I. PMNs in washed whole blood were then an alyzed for phorbol myristate acetate (PMA)-stimulated CD11b, CD35, and CD16 expressions and production of reactive oxygen intermediates (ROI ), as well as phagocytosis with/without anti-CD11b antibody. IGF-I enh anced PMN expressions of CD11b and CD35, but not CD16, stimulated with PMA. Both hormones enhanced phagocytosis, which was abrogated by anti -CD11b antibody, and intracellular ROI production by PMNs. These resul ts indicate that both GH and IGF-I augment human PMN bactericidal capa city, via increased phagocytosis and intracellular ROI production. Pre servation of PMN viability by GH and enhanced complement receptor expr ession by IGF-I may also be associated with augmented PMN bactericidal capacity, Although PMN activation has potentially harmful aspects, th ese results encourage additional studies to confirm the clinical relev ance of exogenous GH or IGF-I for the prevention or management of sept ic complications in perioperative or critically ill patients especiall y with low circulating GH and/or IGF-I levels.