REACTIVITY OF CLONED, EXPRESSED HUMAN FC-GAMMA-RIII ISOFORMS WITH MONOCLONAL-ANTIBODIES WHICH DISTINGUISH CELL-TYPE-SPECIFIC AND ALLELIC FORMS OF FC-GAMMA-RIII

We have Isolated and expressed a cDNA encoding human NK cell FcγRIII. The NK cell cDNA differs from the neutrophil FcγRIII cDNA by a number of point mutations and encodes an additional 21 amino acids at Its C-terminus. When transiently expressed neutrophil and NK cell FcγRIII were digested with N-glycanase, deglycosylated neutrophil FcγRIII had a more rapid electrophoretic mobility than NK cell FcγRIII, as is observed for the human FcγRIII isoforms on normal cells. The neutrophil and NK cell FcγRIII Isoforms apparently result from cell-type specific expression of different forms of FcγRIII mRNA. A Taql RFLP was also found for human FcγRIII. Monoclonal antibodies which have been used to distinguish the neutrophil and NK cell FcγRIII Isoforms and the NA1 and NA2 alleles of human neutrophil FcγRIII were employed to study the expression of two FcγRIII cDNA clones derived from neutrophlls and NK cells. FcγRIII encoded by the neutrophil-derlved cDNA reacts with the monoclonal antibody CLBgran11, while the NK-cell FcγRIII cDNA expresses the Fc receptor which carries an antigenic determinant recognized by the antibody GRM1. Characterization of hybrid FcγRIII constructed by interchange of restriction fragments between the neutrophil and NK cell cDNAs allowed localization of antigenic determiants recognized by the monoclonal antibodies. © 1990 Oxford University Press.