Cloning and characterization of an immunoglobulin A Fc receptor from cattle

Here, we describe the cloning, sequencing and characterization of an immunoglobulin A (IgA) Fc receptor from cattle (bFcαR). By screening a translated EST database with the protein sequence of the human IgA Fc receptor (CD89) we identified a putative bovine homologue. Subsequent polymerase chain reaction (PCR) amplification confirmed that the identified full-length cDNA was expressed in bovine cells. COS-1 cells transfected with a plasmid containing the cloned cDNA bound to beads coated with either bovine or human IgA, but not to beads coated with bovine IgG2 or human IgG. The bFcαR cDNA is 873 nucleotides long and is predicted to encode a 269 amino-acid transmembrane glycoprotein composed of two immunoglobulin-like extracellular domains, a transmembrane region and a short cytoplasmic tail devoid of known signalling motifs. Genetically, bFcαR is more closely related to CD89, bFcγ2R, NKp46, and the KIR and LILR gene families than to other FcRs. Moreover, the bFcαR gene maps to the bovine leucocyte receptor complex on chromosome 18. Identification of the bFcαR will aid in the understanding of IgA-FcαR interactions, and may facilitate the isolation of FcαR from other species.