B lymphoma cells can present antigen targeted by AgAbs to CD4⁺ T cells. T-cell recognition assays were performed using B lymphoma cell lines HLA-matched for CD4⁺ T cells specific to either the EBNA3C 3H10 or EBNA3B B9 epitope. B lymphoma cells including Awia, Yakobo, AG876, and DG75 were incubated with various amounts of αCD-21, -20, -19, or -22 antibodies. B lymphoma cells were incubated for 1 hour with appropriate peptide controls (100 pg, 1 ng, 10 ng, 100 ng, and 1 μg, corresponding to 500 pg/mL, 5 ng/mL, 50 ng/mL, 500 ng/mL, and 5 μg/mL, respectively; gray bars) or for 24 hours with either medium only, or with antibodies containing epitopes (10 pg, 100 pg, 1 ng, and 10 ng, corresponding to 50 pg/mL, 500 pg/mL, 5 ng/mL, and 50 ng/mL, respectively) or containing no epitopes (10 ng, corresponding to 50 ng/mL). EBV epitope–specific CD4⁺ T cells were incubated with these target cells at an E:T cell ratio of 2:1. T-cell activity was determined after 18 hours by measuring IFN-γ secretion by ELISA. Results are given in picograms/milliliter. For each chart, data represent triplicate values and error bars indicate standard deviations. One representative experiment of at least 3 is shown.