Differential expression of Fcγ RIIA, Fcγ RIIB and Fcγ RIIC in hematopoietic cells: Analysis of transcripts

Abstract

Fcγ receptors (Fcγ R) are glycoproteins that function in the immune response through their ability to bind the Fc portion of immunoglobulin G. Of the three human Fcγ R classes, Fcγ RII is most widely distributed among hematopoietic cells and is the only Fcγ R class present on platelets and megakaryocytes. There are three different genes coding for Fcγ RII: Fcγ RIIA, Fcγ RIIB and Fcγ RIIC. Alternative splicing of at least two of these genes results in the production of multiple transcripts. Combining Northern blot analysis with reverse transcription-PCR, we analyzed steady state levels of Fcγ RII mRNA in the megakaryocytic, myeloid and lymphoid lineages. We determined that megakaryocytic cells predominantly contain Fcγ RIIA mRNA; Fcγ RIIA transcripts with and without the transmembrane exon (Fcγ RIIa1 and Fcγ RIIa2, respectively) are present in comparable amounts. In contrast, B lymphocytes do not express Fcγ RIIA mRNAs, but do contain both Fcγ RIIB transcripts, Fcγ RIIb1 and Fcγ RIIb2, as well as the Fcγ RIIC transcript, Fcγ RIIc. Myelomonocytic cells contain mRNAs from all three Fcγ RII genes, predominantly the Fcγ RIIa1 transcript, both Fcγ RIIb1 and Fcγ RIIb2 transcripts and Fcγ RIIc. Lineage-specific expression of the Fcγ RII genes implies both differential regulation of expression and differential function in diverse cells.