Augmented GVHD severity and fibrosis scores in CD19^−/− donor-transplanted recipients. (A) Representative histograms and numbers of IL-10–producing B220⁺ B cells in wild-type (WT) BALB/c, CD19^−/− BALB/c, WT B10.D2, and CD19^−/− B10.D2 groups (three mice in each group). (B) Female wild-type BALB/c (▪, Control) or CD19^−/− BALB/c (▿, CD19^−/− Recipient) mice were transplanted with TCD BM and splenic T and B cells from wild-type CD19^+/+ B10.D2 mice. (C) Skin scores were monitored every 3 days after BMT. Histopathologic scores and the ratio of trichrome area:total area in (D) the skin and in (E) the lung were analyzed 42 days after BMT. (F) Female wild-type BALB/c mice were transplanted with TCD BM and splenic T cells and B cells from male wild-type B10.D2 (▪, Control) or CD19^−/− B10.D2 (△, CD19^−/− Donor) mice. Skin scores were monitored every 3 days after BMT. (G) Histopathologic scores and the ratio of trichrome area:total area in (H) the skin and in (I) the lung were evaluated 42 days after BMT. Representative photographs and microphotographs were taken 42 days after BMT; 4 to 6 mice per group. *P < .05; **P < .01; ***P < .001.