Contribution of APC subsets to alloAg presentation after BMT. (A) T cell–depleted B6.CD11c.DTR Tg BM was transplanted into irradiated BALB/c mice. Recipients were treated with saline, DT, and/or 120G8 mAb on days 8, 10, and 12, as described in “Methods.” CFSE-labeled TEa Tg cells were adoptively transferred 10 days after transplantation, and alloantigen presentation was quantified by assessment of CFSE dilution in cells recovered from spleen 72 hours later (gated on CD4⁺Vα2⁺Vβ6⁺). FACS dot plots demonstrate the proportions of cDCs and pDCs in splenic light-dense fractions remaining after each treatment. EGFP is driven off the CD11c promoter in B6.CD11c.DTR Tg mice, and as such, donor cDCs are defined as CD11c^high/EGFP⁺ in this system. Data are representative of 5 replicate experiments. (B) Serum IFN-γ levels were measured 3 days after adoptive transfer of TEa T cells by cytokine bead array in BALB/c recipients of B6.CD11c.DTR grafts that were treated with saline or DT. P = .038 (1-tailed), saline versus DT. Error bars represent SEM, n = 9 per group from 2 experiments. FACS plots demonstrate IFN-γ production by day 13 Tg TEa cells ex vivo, as measured by ICC staining after restimulation with soluble CD3 for 4 hours. Representative plots shown from n = 5. (C) Absolute numbers of splenic APCs in DT versus saline-treated recipients at day 13 after transplantation. Error bars represent SEM. For cDCs, n = 8; P < .001, saline versus DT treatment. No significant alteration in F4/80⁺ macrophages, B cells, or pDCs (n = 3-9 per group combined from 2 experiments). (D) Recipients of T cell–depleted MAFIA Tg BM were treated with vehicle (n = 3) or AP20187 ligand (n = 7), as described. Ten days after transplantation, CFSE-labeled TEa Tg cells were adoptively transferred, and alloantigen presentation was quantified, as described in panel A. FACS dot plots demonstrate the proportions of splenic macrophages (F4/80⁺/EGFP⁺) and cDCs (CD11c^high/EGFP⁺) in splenic light-dense fractions remaining after each treatment. MAFIA Tg cells express EGFP driven off the c-fms promoter, thus allowing identification of donor cells after transplantation. (E) T cell–depleted μMT BM was transplanted into irradiated BALB/c recipients. CFSE-labeled TEa Tg cells were adoptively transferred, and alloantigen presentation was examined, as described in panel A. FACS dot plots demonstrate the proportions of donor B cells in whole spleen at day 13 after transplantation. (F) Indices of adoptively transferred TEa T-cell proliferation in allograft recipients as calculated using Modfit software. The dotted line represents the proliferation index in syngeneic recipients where there is no alloantigen presentation. Error bars represent SEM, combined from 7 experiments. Saline treated, n = 10; cDC depleted, n = 12; cDC/pDC and pDC depleted only, n = 8; cDC/macrophage (mφ) depleted, n = 7; B-cell deficient, n = 4. **P < .007; *P = .02 versus saline-treated controls. #P = .03 versus MAFIA recipients treated with vehicle.