Biochemical characterization of the porcine Fc gamma RIII alpha homologue G7.

The monoclonal antibodies G7 and PNK-E demonstrate potent enhancement/induction of porcine natural killer and polymorphonuclear leukocyte (PMN)-mediated tumor cell cytotoxicity and have been documented to exist as a molecular complex on the surface of porcine peripheral blood lymphocytes and PMN. This manuscript describes the biochemical characterization of the G7 molecule, recently identified as a porcine homologue of human Fc gamma RIIIA alpha, isolated from porcine leukocytes. Complete deglycosylation of the 43-kDa G7 molecule using N-glycanase reveals two polypeptides of 27 and 31 kDa in the majority of samples. V8 protease peptide mapping reveals structural similarities between the polypeptides and indicates the two polypeptides representing G7 isoforms. The previously described association of PNK-E with G7 and the coexpression of multiple G7 isoforms on porcine leukocytes suggest the presence of a novel Fc gamma RIII alpha molecular complex in the porcine system.