Effective priming of naive CD4+ T cells by B-cell lymphomas occurs in the absence of cross-presentation. BALB/c SCID (left panel) or C57BL/6 SCID (right panel) mice received 1 × 106 naive anti-HA CD4+ TCR transgenic T cells from F1 donors given intravenously. One day later, half the animals in each group were challenged with 1 × 106 A20HA tumor cells given intravenously. Three weeks after tumor challenge, all the animals were killed and T cells were purified from their spleens. (A) T cells were analyzed by 2-color flow cytometry staining for CD4 compared with anti-HA TCR clonotype (mAb 6.5). Three mice were included per group. Values represent mean ± SE of percentage of T cells expressing the clonotypic TCR. Shown is a representative experiment of 3 independent experiments with similar results. Purified T cells (4 × 104/well) from the mice in panel A were mixed with fresh splenocytes (8 × 104/well) from F1 mice to which 12.5 μg HA peptide was or was not added. Forty-eight hours later, supernatants were collected and assayed for IL-2 (B) or IFN-γ (C) by ELISA. Data represent mean ± SE of cytokine production (pg/mL) per well from 3 mice in each group. Asterisks indicate statistically significant differences between tumor-bearing and tumor-free mice (*P < .05; **P < .01). Shown is a representative experiment of 3 independent experiments with similar results.
