Lysis of LCL and B-lymphoma targets by LCL-specific clones P1c4, N1c3, N1c9 and by clone P2c2 specific for the EBNA2_276-295 PRS epitope. (A) Twelve-hour chromium release assays were conducted with HLA class II–matched (auto) and mismatched (allo) LCL targets. Results are expressed as the percentage of specific chromium release from the target cells at effector-to-target ratios of 2.5:1, 5:1, and 10:1. (B) Results of similar assays conducted at an effector-to-target ratio of 10:1, either when both effector and targets were unmanipulated, or when target cells were preexposed to 100 nM Con A for 1 hour after labeling with ⁵¹Cr, or when effector cells were preincubated with 100 ng/mL CD95 Fas (blocking) mAb ZB4 (Immunotech) for 2 hours before the assay. These results are representative of those seen on 3 occasions of testing.