LCLs present antigen targeted by AgAb treatment to CD4⁺ T cells. Multiple T-cell recognition assays were performed using LCLs pulsed with various amounts of αCD-21, -20, -19, or -22 antibodies fused with different EBV epitopes, including (A) EBNA3C 5H11, (B) EBNA3C 3H10, (Ci-Cii) EBNA3B B9, and (D) EBNA2 5A11 (αCD21 antibodies only for EBNA2 epitope). LCLs, HLA-matched with EBV-specific CD4⁺ T-cell clones, were incubated for 24 hours either 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 in A,B,Ci,D), 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). Panel A also includes the results of a T-cell assay performed with the anti–CD21-5H11 AgAb isotype control, whereas panel Cii shows an experiment performed with a matched T-cell clone that recognizes the influenza epitope M1 (gray bars in Cii). 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.