Identification of a monoclonal antibody reactive with the bovine orthologue of CD3 (BoCD3).

A monoclonal antibody (mAb), MM1A, that identifies a molecule expressed on a large percentage of bovine lymphocytes (60-80%) was examined to determine its specificity. Two and three colour immunofluorescence analysis using flow cytometry revealed the molecule is highly expressed on all CD4+ and CD8+ lymphocytes and lymphocytes that express WC1 and the gamma/delta TCR. In contrast to mAbs reactive with BoCD5, MM1A did not react with B lymphocytes. Biochemical analysis revealed that the mAb immunoprecipitates a molecular complex comprising a set of peptides with M(r) approximately 12, 16, 22, 32, 36, and 44 kDa under reducing conditions and an additional 96 kDa peptide complex under non-reducing conditions. The data indicate that MM1A recognizes the bovine orthologue of CD3 (BoCD3).