Antibody blockade of IL-27p28 signaling mitigates the severity of GVHD. (A-B) Irradiated Balb/c recipients were transplanted with B6 BM alone (●, n = 9), or B6 BM and B6 spleen cells (adjusted to yield an αβ T-cell dose of 0.6 × 10⁶ cells) and treated with either an isotype (Iso) control (▪, n = 15) or p28 antibody (□, n = 15). Overall survival and serial weight curves are depicted. (C) Pathological scores of liver, lung, and colon from Balb/c mice transplanted with B6 BM (black bars, n = 8), or B6 BM and B6 spleen cells and treated with either isotype control (light gray bars, n = 15) or p28 antibody (dark gray bars, n = 13-15) 4 weeks posttransplantation. (D) Representative hematoxylin and eosin–stained sections of the liver, lung, and colon from animals transplanted with B6 BM and spleen cells and then treated with isotype control or p28 antibody as in panel C. Arrows denote areas of periportal and perivascular lymphocytic infiltration, respectively. Original magnification is ×50 for liver and lung, and ×100 for colon photomicrographs. (E-F) Balb/c recipients were transplanted with B6 BM alone (black bars, n = 6-8) or B6 BM and B6 spleen cells and treated with either an isotype control (light gray bars, n = 14-15) or p28 antibody (dark gray bars, n = 14-15). The absolute number of donor-derived CD4⁺ and CD8⁺ T cells (E) and CD4⁺ and CD8⁺ T cells that secreted IFN-γ (F) in the liver, lung, and colon 14 days posttransplantation is depicted. (G-H) Lethally irradiated Balb.B mice were transplanted with B6 BM alone (●, n = 9) or B6 BM and B6 spleen cells (adjusted to yield an αβ T-cell dose of 6 × 10⁶ cells) and then treated with an isotype control (▪, n = 15) or p28 (□, n = 15) antibody. Overall survival and serial weight curves are depicted. Results are from 2 to 3 experiments in all panels. *P < .05, **P < .01, ***P < .001.