The effect of CD8⁺T-APCs on effector CTLs is mediated by tumor-derived pMHC.

(A) Ova-expressing EG7 and parental EL4 target cell lines (Left column) and target-entrained CD8⁺T-APC (generated following co-culture of OT-I CD8⁺ T cells with designated targets, right column) were labeled with Ova_257–264/H-2Kb-specific mAb (black histogram). Grey histogram, background staining with isotype control antibody. (B) Proliferation of OT-I CD8⁺ T cells stimulated with CD8⁺T-APCs. CFSE-labeled OT-I T cells were left untreated (no target) or co-cultured with the following T-APCs: OT-I CD8⁺ pre-incubated with EL4 (EL4) or OT-I CD8⁺ pre-incubated with EG7 cells (EG7). ConA stimulation was used as positive control (right). Scale bars, proliferating lymphocytes that divided at least twice. Numbers, percentage of dividing CD8⁺ T cells. Data are representative of two independent experiments.