B-cell depletion by anti-CD20 therapy is not sufficient to prevent cGVHD and associated BOS. cGVHD was established in B10.BR mice transplanted with WT B6 BM and WT B6 spleen cells, and mice were treated with anti-CD20 or irrelevant mouse IgG1 antibody from day 28 to day 56. (A) PFTs for mice treated with irrelevant or anti-CD20 antibody. (B) Number of B cells purified from the spleens of mice on day 56. (C) Trichrome deposition and (D) Ig deposition in the lungs of mice harvested on day 56. (E) Number of CD138⁺ CD19 low plasma cells in the BM of D60 transplanted mice. (F) Representative images of frozen lung tissues stained with anti-CD19 FITC and 4,6 diamidino-2-phenylindole. Representative data from 2 experiments; n = 8 mice per group. *P < 0.5; **P < .01; ***P < .001.