In vitro murine T-cell proliferation using HSVB7.1 amplicon-infected CHO or EL4 cells. Splenocytes from adult C57BL/6 mice were harvested and T cells were enriched as described in Materials and Methods. Purified T cells were cultured in triplicate wells with HSVB7.1-infected CHO or EL4 cells. CHO-B7.1 or EL4-B7.1 cells stably transduced with a retroviral vector expressing human B7.1 were used as positive controls. HSVlac-infected or parental EL4 or CHO cells were used as negative controls. Antimurine CD3 antibody (2C11) at a final 1:50 dilution or PMA (10 ng/mL) with Ionophore (0.1 ng/mL) was added as indicated. After 72 hours, the cells were pulsed with³H-thymidine and harvested and incorporated radioactivity was measured as described in Materials and Methods. The results are represented as the mean counts per minute (cpm) from triplicate cultures ± standard deviation.