Characterization and expression of monoclonal antibody-defined molecules on resting and activated bovine αβ, γδ T and NK cells.

Monoclonal antibodies (mAbs) specific for leukocyte differentiation molecules (LDMs) were developed during the past few decades to expand reagents for research in ruminants, pigs, and horses. The specificity of some of the mAb-defined molecules was determined through participation in international workshops. Other molecules identified with mAbs during this time, and more recently with mAbs developed after the workshops, have remained partially characterized. Efforts are now underway to characterize the specificity of these mAbs. As reported here, flow cytometry (FC) was used to screen two sets of hybridomas to determine how many of the hybridomas produce mAbs that detect molecules with up-regulated expression on activated lymphocytes or NK cells. Thirty four hybridomas were identified. Comparison of the patterns of reactivity of the mAbs showed some of the mAbs formed clusters that recognize 5 different molecules. FC showed one cluster recognized CD25. Use of mass spectrometry showed 4 clusters recognized orthologues of CD26, CD50, gp96 and signaling lymphocytic activation molecule family member 9 (SLAMF9). Verification and documentation that CD26, CD50, and SLAMF9 were only up-regulated on activated cells was obtained with PBMC from calves vaccinated with a Mycobacterium avium paratuberculosis mutant, Map-relA. CD26 and CD50 were up-regulated on NK cells, CD4 and CD8 T cells and γδ T cells. SLAMF9 was only up-regulated on CD4, CD8, and γδ T cells. gp96 was detected on granulocytes, monocytes and activated NK cells. Detection was attributable to the binding of gp96 to its receptor CD91.