CD51 (α(v)) is an integrin chain that associates with multiple β integrin chains to form different receptor complexes that mediate important human processes. Pigs show substantial physiological, immunological and anatomical similarities to humans, and are therefore a good model system to study immunological and pathological processes. Here we report the cloning and characterization of two cDNAs produced by alternative splicing that encode two different porcine CD51 proteins that differ in five amino acid residues. Pig CD51 cDNAs encode polypeptides of 1046 or 1041 amino acid residues, respectively, that share with other mammalian homologous proteins a high percentage amino acid identity and the functional domains. Expression analysis of CD51 was carried out at two different levels. RT-PCR analysis revealed that both CD51 transcripts were expressed ubiquitously but heterogeneously, with the exception of some platelets in which only the smallest CD51 transcript was detected. A specific monoclonal antibody against a pig CD51 recombinant protein was made and used in the immunohistochemical localization of CD51 proteins. It showed that CD51 was mainly expressed in hematopoietic cells of myeloid linage, epithelial and endothelial cells, osteoclasts, nervous fibers and smooth muscle. Adhesion assays showed that in the presence of Mn(++) pig α(v)-CHO-B2 transfected cells increased their attachment to fibronectin and vitonectin, but not to fibrinogen. Finally, we localized the CD51 gene on the porcine chromosome 15 (SSC15), q23-q26.
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