Cytotoxic T lymphocyte assays with blocking antibodies. Percent specific lysis of target cells is depicted on the y-axis. Pooled splenocytes from two animals resistant to autologous tumor challenge from the treatment groups identified on the x-axis at an effector to target ratio 100:1. Anti-CD4 or anti-CD8 antibodies (Pharmingen) were added at 30 μL/well to inhibit activity. The data represent the mean ± SD of three determinations.