B-cell–specific XBP-1 impairs pulmonary function in a BO model of cGVHD. B10.BR recipients were treated twice with cyclophosphamide (120 mg/kg) 1 time per day on days −3, −2, and sublethally irradiated on day −1 before transplant. On day 0, mice were transplanted with TCD-BM (5 × 10⁶ per mouse) from XBP-1^flox/floxCD19Cre⁻ (n = 10) or XBP-1^flox/floxCD19Cre⁺ donors (n = 9) on a B6 background with (n = 19) or without (n = 4) whole splenocytes (Sp) at 0.15 × 10⁶ per mouse. Mice were monitored for body weight loss until experiment endpoint (A), where recipients were anesthetized, given tracheostomy, and subjected to lung function analysis using a SciReq flexiVent device 28 days after transplant (B-C). Data from panels B and C are pooled from 2 separate experiments. Panel A shows representative body weight loss from 2 replicate experiments. Statistics were performed using 2-tailed Student t tests of each indicated time point, where P < .05 indicates statistical significance and an asterisk indicates statistical significance between XBP-1^flox/floxCD19Cre⁻ and XBP-1^flox/floxCD19Cre⁺ groups: *P < .05. BM, bone marrow; Crs, compliance; Cst, quasistatic compliance; Rrs, airway resistance of the respiratory system as a whole.