Nonspecific cytotoxic cells in fish ( [formula omitted][formula omitted]) V. Metabolic requirements of lysis

Abstract

The mechanisms of lysis of nonspecific cytotoxic cells (NCC) from the channel catfish ( Ictalurus punctatus ) were studied by determining the effects of various inhibitors of cellular metabolism on cytolysis of NC-37 human lymphoma target cells. Inhibition of NCC-mediated lysis by dinitrophenol (DNP) and sodium azide (NaN 3) indicated a requirement for cellular energy metabolism. Cytochalasin B, an inhibitor of microfilaments, and monensin, an inhibitor of cellular secretion, both prevented lysis by NCC. Three microtubule inhibitors, vinblastine sulfate, colchicine, and demecolcine, all inhibited target cell lysis. Two divalent cation chelators, EDTA and EGTA, blocked NCC activity. Elimination of both Ca 2+ and Mg 2+ by EDTA prevented target cell binding and killing. Selective removal of Ca 2+ by EGTA prevented killing but did not block target cell binding. These results indicated that nonspecific cytotoxicity in fish is an active process which requires cell movement and an intact secretory apparatus. The mechanisms of cytolysis by NCC were found (except for the requirement of microtubules) to be analogous to those of mammalian NK cells. Combined with morphological studies, these data strongly suggest that a phylogenetic relationship exists between these effector cells.