Leukemia-derived cytokines may contribute to phenotypic T cell exhaustion. (A) Serum was collected from leukemia-bearing mice 12 days after TCF3/PBX1.3 injection. Cytokines were measured by multiplex assay. Unirradiated C57Bl/6 mice were used as controls. (B) Serum was collected from MLL-AF4–bearing mice (conditioned with 250 cGy irradiation prior to injection) as in panel A and serum analyzed for cytokines. Irradiated mice were used as controls. (C) TCF3/PBX1.3.3 was cultured in the presence of IL-6 (200 µg /mL), IL-10 (100 µg /mL), TNF-α (100 µg/mL), or all 3 cytokines combined. Tim3 expression was evaluated by flow cytometry after 2 or 3 days of culture.