Donor DC–derived IL-6 maintains alloreactive T-cell expansion and differentiation. (A) BALB/c mice were lethally irradiated (900 cGy) and received donor grafts containing 10 × 10⁶ TCD BM and 0.2 × 10⁶ T cells from either CD11c.Cre⁻ × IL-6^fl or CD11c.Cre⁺ × IL-6^fl mice, and peripheral blood serum IL-6 levels were monitored over 28 days (n = 8-12 mice per group from 2 experiments). (B) BALB/c mice were lethally irradiated and received transplants of 10 × 10⁶ TCD BM from either CD11c^Cre, CD11c^Cre × IL-6R^fl, or CD11c^Cre × IL-6^fl mice, along with 0.2 × 10⁶ B6 wild-type (B6.WT) T cells. On day 12 after transplantation, 2.5 × 10⁶ TEa^luc+ cells were injected and 3 days later quantified in the GI tract. (C) Representative images of bioluminescence imaging (BLI) in the GI tract, mLNs, and spleen are shown. (D) Quantification of BLI in the mLNs (n = 13-15 mice per group from 3 experiments). (E) Quantification of total TEa^luc+ (CD45.1⁺Vβ6⁺Vα2⁺) cells in the mLNs by flow cytometry. (F-G) Representative contour plots (concatenated from 4 mice per group) (F) and frequency and enumeration (G) of Th17 (IL-17⁺), Th22 (IL-22⁺IL-17⁻), and IFNγ and TNF expression by TEa^luc+ cells from the mLNs (n = 9 mice per group from 2 experiments). Data presented as mean ± standard error of the mean. *P < .05, **P < .01. TBI, total-body irradiation.