Donor-derived T_H1 and T_H17 cells that mediate autoimmunity emerge during acute GVHD. (A) Lethally irradiated (900 cGy) Balb/c mice received transplants of TCD Balb BM plus 3 × 10⁵ Balb spleen cells (syngeneic) (□) or TCD B6 BM (10 × 10⁶) plus 3 × 10⁵ B6 spleen cells (allogeneic) (■). Mice in both cohorts were bled 21 days after transplantation, and serum was analyzed for presence of IL-17, G-CSF, TNF-α, IL-6, IL-1β, and IFN-γ. Data are presented as the mean plus or minus SEM and are cumulative results from 2 experiments. (B) Lethally irradiated Balb mice were transplanted with TCD BM (10 × 10⁶) plus 3 × 10⁵ B6 spleen cells. At 20 days after transplantation, CD4⁺ T cells were purified from pooled spleen cell suspensions by magnetic bead separation. Cells were then restimulated with PMA and ionomycin in the presence of GolgiStop and then intracellularly stained with IFN-γ, IL-17, or IL-4–specific antibodies. Dot plots show the percentage of CD4⁺ T cells that were positive for each of these cytokines.