Monoclonal antibodies to a high molecular weight isoform of porcine CD45: biochemical and tissue distribution analyses.

This report describes the obtention and characterization of two monoclonal antibodies (mAbs), 6E3/7 [mAb 6E3/7 was submitted to the Second International Swine CD Workshop, where it has been assigned to CD45R] and 3C3/9, which recognize the isoform of highest molecular weight of porcine CD45. This conclusion is based on their cell reactivity and tissue distribution, identical to that reported for the human high molecular weight isoform of CD45, and on data from immunoprecipitation and immunoblotting analyses which show that these mAbs react with the largest polypeptide of those precipitated by mAb 2A5, that recognizes an epitope shared by all CD45 isoforms. These mAbs react with 60% of peripheral blood mononuclear cells (PBMC) but not with alveolar macrophages, granulocytes, platelets or erythrocytes. Antigen expression on PBMC is heterogeneous and is reduced after in vitro activation with mitogens. B cells and CD8+ T cells express more antigen than CD4+ T cells. Using immunoperoxidase techniques, the antigen was detected on B cell areas of lymph nodes and Peyer's patches, and on a subpopulation of medullary thymocytes. These mAbs will be useful reagents for functional and phenotypic analysis of porcine lymphoid cell populations by flow cytometry and immunohistochemistry.