In vivo antitumor efficacy of 19mz⁺ T cells is dependent on continued IL-12 activation in vivo, and requires the presence of both CD4 and CD8 T cells subsets. (A) Similar to 19mz⁺ and Pmz/IL-12⁺ T-cell therapy, treatment of C57BL6(mCD19^−/−hCD19^+/−) mice bearing systemic EL4(hCD19) tumors with 19mz⁺ T cells cultured ex vivo with exogenous IL-12, in contrast to 19mz/IL-12⁺ T-cell treated mice failed to induce either B-cell aplasias or mediate tumor eradication (B). (C) Sorted CD4⁺ 19mz/IL-12⁺ T cells failed to induce B-cell aplasias in EL4(hCD19mCD80) tumor-bearing mice, in contrast to CD8⁺ 19mz/IL-12⁺ T cells, which induced a partial but significant B-cell aplasia and bulk 19mz/IL-12⁺ T cells, which induced significant B-cell aplasias. (D) In addition, in contrast to bulk 19mz/IL-12⁺ T cells, treatment with either sorted CD4⁺ or CD8⁺ 19mz/IL-12⁺ T cells alone failed to eradicate systemic EL4(hCD19⁺) tumors. Results shown are representative of 2 independent experiments with similar results.