CHARACTERIZATION OF THE CYTOLYTIC TRIGGER MOLECULES G7 PNK-E AS A MOLECULAR-COMPLEX ON THE SURFACE OF PORCINE PHAGOCYTES/

G7 and PNK-E mAbs recognize distinct porcine NK cell and granulocyte f unction-associated molecules that enhance and induce a significant cyt olytic response against tumor cell targets through a mechanism of redi rected cytotoxicity, The present study shows that the G7 and PNK-E mol ecules are present on the surface of porcine neutrophils, monocytes, a nd pulmonary alveolar macrophages as a physically and functionally ass ociated cytolytic trigger molecular complex. Two-color flow cytometric analysis demonstrates that most, if not all, neutrophils are G7 and P NK-E antigen positive, In contrast, monocytes and PAM contain both G7 and PNK-E positive as well as G7 positive and PNK-E negative subpopula tions. mAb binding competition experiments indicate that pretreatment of phagocytes with G7 mAb can block subsequent binding by PNK-E mAb, s uggesting that these antigens are physically associated on the surface of porcine phagocytes. Fluorescent cocapping experiments utilizing G7 and PNK-E mAbs clearly demonstrate a physical association between G7 and PNK-E antigens present on the surface of porcine neutrophils, Pret reatment of phagocytes with F(ab')(2) fragments of G7 and PNK-E mAbs s hows that F(ab')(2) G7 mAb blocks subsequent induction of phagocyte-me diated tumor cell cytotoxicity by whole PNK-E mAb but pretreatment wit h F(ab')(2) PNK-E does not block subsequent induction of phagocyte-med iated tumor cell cytotoxicity by whole G7 mAb, In addition, pretreatme nt of neutrophils and mononuclear phagocytes with F(ab')(2) fragments of G7 mAb blocks subsequent whole PNK-E mAb-dependent activation of a phagocytic cell intracellular oxidative burst response but pretreatmen t with F(ab')(2) PNK-E does not block subsequent G7 mAb-dependent acti vation of a phagocytic cell intracellular oxidative burst response, Th ese data reinforce a physical and functional association between the G 7 and PNK-E molecules, Recent identification of the G7 antigen as the porcine homolog of Fc gamma RIII indicates that the G7 and PNK-E mAbs recognize a unique and previously uncharacterized Fc gamma R cytolytic trigger molecular complex present on the surface of porcine neutrophi ls,monocytes, and PAM. (C) 1995 Academic Press, Inc.