Chemokine receptor CXCR5 on donor mature T cells is necessary for cGVHD. B10.BR mice were transplanted with WT B6 BM and WT B6 T cells or B6 CXCR5 KO T cells. (A) Mice were evaluated for pulmonary function. (B) Lung sections were stained with FITC-conjugated anti-mouse Ig, and the area of Ig deposition was measured as shown in (C) representative images. (D) Lungs of mice were stained with trichrome, and the ratio of collagen stain to total stain was measured surrounding the bronchioles as shown in (E) representative images. Representative data from 3 experiments; n = 8 mice per group. *P < .05; **P < .01; ***P < .001.