Identification and quantitation of bovine T cell antigen with enzyme-linked immunosorbent assay (ELISA)

The enzyme-linked immunosorbent assay (ELISA) was used to identify and quantitate T cell antigen(s) in bovine thymocytes and peripheral blood T cells. The ELISA, employing non-ionic detergent-solubilized lymphocyte membranes as antigen, and goat anti-bovine thymocyte serum (GABTS) and horseradish peroxidase-conjugated rabbit anti-goat immunoglobulin (PORAG) as direct and indirect reactants, respectively, showed that thymocytes and peripheral blood T cells separated by erythrocyte-antibody-complement (EAC) rosetting technique had high concentrations of T cell antigen. In contrast, bone marrow cells and EAC-positive peripheral blood B cells had minimal T cell antigen. 92.0 +/- 3.5% of EAC-positive bovine lymphocytes were found to be B cells and 89.5 +/- 5.8% of EAC-negative lymphocytes T cells, as determined by SmIg and anti-T cell immunofluorescence (IF) techniques. In both IF and ELISA, pre-absorption of rabbit anti-goat IgG serum was needed to obviate cross-reactions with bovine B cells. A competitive ELISA developed for quantitating T cell antigens, showed that peripheral blood T cells contained only 46% of the antigen present in thymocytes.