Treatment with anti-CSF1R exacerbates acute GVHD. (A) Survival by Kaplan-Meier analysis. Irradiated anti-CSF1R and rat IgG mAb-treated B6D2F1 recipients were transplanted with BM and T cells from C57Bl/6 mice as described in supplemental Methods (rat IgG allo and anti-CSF1R allo; n = 21/treatment). Irradiated anti-CSF1R–treated B6D2F1 received TCD BM and served as non-GVHD controls (n = 8). ***P < .0001, rat IgG allo vs anti-CSF1R allo. (B) F4/80 staining in liver, colon, and small gut taken from rat IgG allo and anti-CSF1R allo recipients 7 days after transplantation. (C) Liver and gut histopathology was determined by semiquantitative histology as described in supplemental Methods. (D) Unfractionated splenocytes from rat IgG allo and anti-CSF1R allo recipients 7 days after transplantation were cultured with CD3 and IFNγ and TNF determined in 24-hour tissue-culture supernatant or (E) cultured with CD3 and brefeldin and IFNγ and TNF measured by intracellular cytokine staining. (F) CD4⁺FoxP3⁻ T effectors and CD4⁺FoxP3⁺ T_reg were enumerated in spleens and lymph nodes from rat IgG allo and anti-CSF1R allo recipients 7 days after transplantation. In all histograms, the white bar represents rat IgG allo recipients; the black bar, anti-CSF1R allo recipients; and the hatched bar, anti-CSF1R TCD recipients.