PDC depletion around the time of DLI exacerbates GVHD after alloHSCT of TCD STAT1−/− BM. (A) Lethally irradiated recipients received TCD miHA-mismatched BM from STAT1+/+ or STAT1−/− donors (129 → C3H.SW), and on day +14, 20 × 106 DLI was administered to induce GVHD. Some recipients did not receive a DLI as a negative GVHD control. All groups were treated with either IgG2b or PDCA-1 moAb on day +12, 14, 16, 18, and 20 to deplete pDCs. (B) Some recipients were sacrificed on day +21 for enumeration of pDCs in the spleen. Treatment with PDCA moAb depleted about 71% of pDCs in the spleen as determined by flow cytometry. (C) All alloHSCT recipients were followed for clinical GVHD scores. (D) On day +40, splenic B220+ counts were enumerated by flow cytometry. (E) Lethally irradiated recipients were transplanted with STAT1+/+ or STAT1−/− BM on Day +0, then on day +14 they were given a DLI with concurrent 5 × 105 STAT1+/+ pDCs or STAT1−/− pDCs and were followed for GVHD-associated weight loss. N = 5 to 8 mice/group, data are representative from 1 of 2 similar experiments. **P < .01, ***P < .001.
