Molecular cloning and expression analysis of pig CD79α

The CD79α (immunoglobulin α, Igα), a part of B cell receptor (BCR) complex, forms a heterodimer with CD79β (Igβ) and plays an important role in the B cell signaling. In this study, we have cloned pig Cd79a cDNA using RT-PCR and determined the complete cDNA sequence of pig Cd79a. Pig Cd79a cDNA contains an open reading frame (672 bp) encoding 223 amino acids. The putative amino acid identity of pig CD79α with those of human, cattle and mouse are 70.4, 81.4, and 67.7%, respectively. Alignment of the CD79α amino acid sequence with those of mammalian species showed that the extracellular domain is the most divergent, whereas transmembrane region and cytoplasmic tail including immunoreceptor tyrosine-based activation motif (ITAM) are largely conserved. Pig Cd79a mRNA was detected mainly in lymphoid tissues by RT-PCR. The highest level of Cd79a mRNA expression was observed in mesenteric lymph node and spleen. Relatively low level of Cd79a mRNA expression was observed in lung, thymus and small intestine. The lowest level of Cd79a mRNA expression was observed in large intestine. Flow cytometry analyses demonstrated that human CD79α antibody recognizes a CD79α in pig B cells. Further, immunohistochemistry analysis using human CD79α antibody on pig spleen was revealed that CD79α is strongly expressed in the follicular mantle zone rather than in the germinal center. Future study will be focused on defining the functional role of CD79α during the course of pig infectious diseases and the formation of neoplasm.