Biochemical and functional characterization of 8-10C5 (gp120,90), a novel molecule on the surface of bovine T leucocytes.

An unclustered molecule, 8-10C5, present on bovine leucocytes, was characterized using a monoclonal antibody (mAb) prepared at the University of Wisconsin-Madison, and the functional and biochemical characteristics of that molecule compared to defined molecules. This molecule was present on a large percentage of peripheral blood cells (84%), including T and B lymphocytes, monocytes and neutrophils, but was absent from immature thymocytes. mAb 8-10C5 blocked proliferation to alloantigen and bovine herpesvirus-1; however, antibody to the 8-10C5 molecule was unable to stimulate proliferation alone or in combination with PMA or a cross-linking agent. These results indicate that this molecule has a role in T-cell activation, but probably not signal transduction. mAb 8-10C5 was unable to block cytotoxic T lymphocyte (CTL) or natural killer (NK)-like lysis. mAb 8-10C5 identifies a non-covalently bound heterodimer present on most peripheral lymphocytes with a molecular weight (MW) of 120,000 for the alpha chain (10% glycosylation) and 90,000 MW for the beta chain (16% glycosylation). The beta chain is an acidic molecule (pI = 4.5-5.0). Biochemical studies included the CD2 and CD5 molecules and further demonstrated their similarity to equivalent molecules in other species, confirming the phylogenetic importance of these molecules in immune responses. This functional and biochemical information will allow further characterization of these molecules at the RNA and DNA levels.