MiR-31 is upregulated in allogeneic T cells and enhances their pathogenicity in cGVHD induction in mice. (A-B) T cells isolated from Ly5.1⁺ B6 mice were injected together with T cell–depleted (TCD; Ly5.2⁺) BM into lethally irradiated BALB/c (allogeneic [Allo]; 700 cGy) or Ly5.2⁺ B6 (syngeneic [Syn]; 1200 cGy) mice. (A) MiR expression was evaluated in H2K^b+Ly5.1⁺ donor T cells by oligonucleotide arrays on day 14. The heat map represents the log2 value of the relative amount of each miR. (B) The messenger RNA expression of miR-31 in naïve T cells and activated donor T cells isolated from Allo or Syn recipients was evaluated by real-time polymerase chain reaction. (C-I) Splenocytes (0.35 × 10⁶) and TCD BM (5 × 10⁶) from WT or miR-31 KO B6 mice were injected into lethally irradiated BALB/c mice. Recipients of WT BM cells only without splenocyte injections served as the no-GVHD control (white circles). Recipient clinical scores and body weight loss were recorded weekly and displayed along the time after BMT (C). Cutaneous pathologic scores (D) and collagen deposition in skin evaluated with Masson’s trichrome stain (E, original magnificaiton ×200) are shown on day 50. Pathologic scores of salivary glands in recipients were recorded on day 60 after BMT (I). (F-H) WT or miR-31 KO T cells (2.75 × 10⁶) plus WT TCD BM were transferred into lethally irradiated B6D2F1 mice. Clinical scores (F), cutaneous pathologic scores (G), and collagen deposition (H, original magnificaiton ×200) are shown on day 50. Data shown are from 1 representative of 3 individual experiments (n = 5-6 mice per group for each experiment). (J-K) B10.BR mice were conditioned with cytoxan (120 mg/kg) and irradiation and then underwent transplantation with WT or miR-31 KO T cells (5 × 10⁴) plus WT TCD BM. Body weight loss (J) and pulmonary compliance, elastance, and constriction analyzed with a flexiVent system (K) are shown on day 50 after BMT. *P < .05, **P < .01.