HUMAN TYPE-II PHOSPHOLIPASE A(2)-INDUCED MAC-1 EXPRESSION ON HUMAN NEUTROPHILS

To investigate the effect of type II phospholipase A(2) (PLA(2)-II) on neutrophil function, we assessed the Mac-1 (CD11b/CD18) expression on human neutrophils by flaw cytometry after incubation of the cells wit h human PLA(2)-II, PLA(2)-II at a concentration of 10 mu g/mL increase d the Mac-1 expression by 150% compared wit unstimulated cells at 30 m in and after, Under these conditions PLA(2)-II increased the exocytosi s from secretory vesicles but not from azurophilic, specific, or gelat inase granules, The results suggest that PLA(2)-II induces translocati on of Mac-1 from the secretory vesicles to the plasma membrane, Tile M ac-1 induction mediated by PLA(2)-II was inhibited by an anti-PLA(2)-I I antibody, which was able to inhibit the catalytic activity, However, the Mac-1 induction by PLA(2)-II was not inhibited by a 5-lipoxygenas e, cyclooxygenase inhibitor, or a platelet-activating factor antagonis t. Thus, we examined the effects of fatty acids and lysophospholipids oil Mac-1 expression, Only arachidonic acid induced Mac-1 expression, These results imply that PLA(2)-II induces Mac-1 expression oil neutro phils via production of arachidonic acid.