CHARACTERIZATION OF RESTING AND PHORBOL ESTER OR CONCANAVALIN A ACTIVATED BOVINE LYMPH-NODE CELLS WITH LEUKOCYTE SPECIFIC MONOCLONAL-ANTIBODIES

Bovine lymph node cells (LNC) have been used as a model to study cell activation and proliferation. Because monoclonal antibodies to bovine lymphoid-specific surface antigens have only recently become available , these cells have not been previously characterized in regard to subp opulations. Furthermore, it was not known how expression of lymphoid d ifferentiation antigens and subset proportionalities might change foll owing different modes of activation of LNC. Therefore, the distributio n of cell-surface differentation antigens in unstimulated LNC as well as in LNC incubated with the mitogen concanavalin A (Con A) or the pho rbol ester, phorbol dibutyrate (PDBU), was measured using a series of leukocyte-specific monoclonal antibodies and flow cytometry. Unstimula ted LNC were found to have similar proportions of T cells, B cells (sI gM positive), and MHC Class II positive cells similar to bovine periph eral blood mononuclear leukocytes (reviewed by Baldwin et al., 1988a). Treatment of the LNC with PDBU or mitogenic doses of Con A induced ch anges in the expression of surface antigens consistent with the change s observed with human and mouse cells after similar activation. Howeve r, these two compounds did not cause identical effects. After treatmen t with PDBU, the percentage of cells expressing CD4 as well as the den sity of surface expression decreased. An increase in the percentage of cells expressing and/or density of surface expression of the pan T ce ll antigens CD2, CD5, CD6, MHC Class II and J5, a T cell activation an tigen, also occurred. PDBU treatment also increased the percentage of CD8 positive cells. The change in CD6 following PDBU treatment has not been reported previously. Con A treatment led to a significant increa se in the percentage of cells bearing CD8, CD6, MHC Class II and J5, b ut it had no effect on the percentages of cells positive for the other T cell markers CD5, CD4, or CD2. Because Con A is a complete mitogen and PDBU is not, the changes observed following Con A stimulation prob ably reflected an expansion of a particular subpopulation. In contrast , PDBU most likely modifies surface antigen expression directly. Neith er treatment affected the B cell subpopulation.