Effect of bovine herpesvirus-1 on expression of interleukin-2 receptors and effect of interleukin-12 on lymphocyte proliferation

Abstract

Expression of the interleukin-2 receptor α chain (IL-2Rα) by peripheral blood mononuclear cells (PBMC) from Holstein calves, both experimentally-infected with bovine herpesvirus-1 (BHV-1) and controls, was measured by flow cytometry. Expression of IL-2Rα was 35% and 23% higher in infected calves than controls, on days 2 and 3 postinfection (PI), respectively. Concurrent with this increase in IL-2Rα expression, a significant decrease ( P < 0.001) was observed in the PHA-induced proliferative responses of PBMC from infected compared with control calves. In vitro treatment with recombinant human (rhu) IL-12 enhanced PHA-induced proliferative responses of PBMC from both infected and control calves. This rhuIL-12 enhancement of mitogen-induced proliferative responses was significant ( P < 0.001) in infected calves on day 2 PI and was sufficient to abrogate the decrease observed due to BHV-1 infection. Since the expression of the β and γ chains of IL-2R was not measured it is difficult to speculate as to the status of high affinity receptor expression during BHV-1 infection. However results of the present study suggest that the decrease in proliferative responses observed during infection may not be due to a decrease in IL-2Rα expression but may possibly be due to a selective down-regulation of signal transduction through IL-2R and/or by modulation of the expression of other cytokines involved in lymphocyte activation and proliferation.