CD4⁺ CD28^−/− donor T cells have a limited capacity to cause GVHD in irradiated (B6 × bm12)F1 recipients. (B6 × bm12)F1 mice were irradiated (700 cGy) and transplanted with CD28^+/+ CD4⁺ cells or CD28^−/− CD4⁺ cells from B6 donors. Irradiated (B6 × bm12)F1 mice were injected with PBS alone as control. (A) Survival curves; (B) Weight curves show the mean body weight for each group. Data were pooled from two replicate experiments.