Fig. 1.

Intravenous administration of CD4 mAbs results in a transient depletion of circulating CD4⁺ T-cells in peripheral blood and loss of proliferative response to BHV-1 antigen. Two groups of three calves were vaccinated with commercial BHV-1 vaccine, and subsequently vaccinated with A22 Iraq FMD commercial vaccine (2–3 weeks later). Each animal received intravenous injections of either an isotype-matched control TRT 3 (a and c) or anti-CD4 (b and d) mAb for a period of 4 days, starting the day before FMD vaccination. At various time points prior to and following FMD vaccination, the percentage of CD4⁺ T-cells in PBMC was determined by flow cytometry after staining the cells with either an anti-CD4 (black bars) or TRT1 isotype control (grey bars) mAb (a and b) and the proliferation of PBMC to heat-inactivated BHV-1(1/100, black bars) or EBTr cell lysate (control antigen, 1/100, grey bars) was assessed by [methyl-³H] thymidine incorporation (c and d). Results are expressed as the mean of determinations from individual calves in each group±sem, n = 3.