Detection of impaired T cell-mediated immune responses to herpesvirus (BHV-1) in cattle

Interleukin 2 (IL-2) functions in the regulation of cell-mediated immune responses both in vivo and in vitro. Therefore, IL-2 production has been studied in patients with immunological disorders to determine the level of the immune defect. However, the cause(s) of low responses to selected antigens by cells from clinically normal individuals has not been examined. The ability of cells from clinically normal individual cattle to produce and respond to IL-2 was investigated as a measure of specific cell-mediated immune response. Cells from the majority of animals (6/7 in a representative experiment) could produce IL-2 in response to mitogen or a specific antigen, Bovine Herpesvirus 1 (BHV-1). Proliferation of lymphocytes from the majority of low responding animals (2/3 and 4/4 in separate experiments) could be restored to a level similar to high responders by the addition of exogenous IL-2 after endogenous IL-2 depletion. IL-2 receptor expression was indirectly assessed by the ability of activated cells to absorb IL-2. One individual's cells were incapable of absorbing exogenous IL-2 and failed to proliferate indicating a lack of activation and expression of receptors. In addition, exogenous IL-2 was able to enhance proliferation of both high and low responders in the presence of endogenous IL-2. These results suggest that proliferation of bovine peripheral blood mononuclear cells is dependent on the presence of IL-2. In addition, IL-2 production can be used to measure specific cell-mediated immune responses.