MicroRNA-17-92 is required for the T-cell and B-cell pathogenicity that drives chronic graft-versus-host disease (cGVHD) after allogeneic bone marrow transplant (BMT), report investigators. Data from cGVHD mouse models showed that, by determining T-cell and B-cell differentiation and function, miR-17-92 is responsible for cGVHD development. Inhibiting miR-17 is a potential therapeutic strategy for preventing cGVHD in BMT patients.