CRK/CRKL^−/−T cells do not cause cGVHD-mediated BO. Conditioned B10.BR mice were transplanted with B6 donor BM only or plus 70 000 WT or CRK/CKRL^−/− T cells. (A) Pulmonary tests including lung resistance, elastance, and compliance suggest CRK/CKRL^−/− donor T cells did not cause cGVHD. (B) Masson’s Trichome staining in lung identified collagen in blue. Quantification of blue areas suggests recipients of CRK/CKRL^−/− donor T had significantly lower collagen deposition the WT T-cell recipients. (C) Immunofluorescence staining of macrophage marker CD68 suggests significantly lower macrophage infiltration in the CRK/CRKL^−/− T recipients. (D-G) Flow cytometry analysis of cell frequencies in GC reactions including (D) Tfh, (E) Tfr, (F) Tfh/Tfr ratio, and (G) GC B cell. GC analysis suggests CRK/CKRL^−/− donor T cells did not induce GC reactions. (H) Immunofluorescence staining of immunoglobulin deposition in the lung. Quantification suggests recipients of CRK/CKRL^−/− donor T cells have lower immunoglobulin deposition. Images were taken by Olympus FV1000 upright confocal at ×200 magnification. Data shown are representative of 2 independent experiments with 5 to 8 mice per group. An unpaired Student t test was used when comparing 2 groups. Significance: *P < .05; **P < .01; ***P < .001; ****P < .0001. KO, knockout.