Isolation and expression of cDNA clones encoding a human receptor for IgG (Fc gamma RII).

Abstract

We have cloned and expressed a cDNA encoding a human receptor for IgG (Fc.gamma.R) from the monocyte cell line U937. The deduced structure is a 35-kD transmembrane protein with homology to the mouse Fc[.gamma.2b/.gamma.1] receptor amino acid sequence of .apprx. 60% in the extracellular domain. The signal sequence is homologous to the mouse Fc.gamma.R.alpha. cDNA clone, while the transmembrane domain shares homology with mouse Fc.gamma.R.beta. cDNAs. The cytoplasmic domain is apparently unique. The extracellular domain shows significant homology to proteins of the Ig gene superfamily, including the human c-fms protooncogene/CSF-1 receptor. Mouse Ltk- cells transfected with the human Fc.gamma.R cDNA express a cell-surface receptor that selectively binds human IgG and is recognized by the anti-Fc.gamma.RII mAb IV.3. Antibodies against peptides derived from the human Fc.gamma.R sequence specifically stain U937 cells, but not an Fc.gamma.RII-bearing B-lymphoblastoid cell line (Daudi). These results identify the human Fc.gamma.RII as the homologue of mouse Fc[.gamma.2b/.gamma.1]R, and provide evidence for heterogeneity of Fc.gamma.RII expressed on monocytes and B cells.