Background and Aim: Chronic graft-versus-host disease (cGVHD) is a major cause of nonrelapse morbidity and mortality following hematopoietic stem cell transplantation (HSCT). alpha-Galactosylceramide (alpha-GC) is a synthetic glycolipid that is recognized by the invariant T-cell receptor of invariant natural killer T (iNKT) cells in a CD1d-restricted manner. Stimulation of iNKT cells by alpha-GC leads to the production of not only immune-stimulatory cytokines but also immune-regulatory cytokines followed by regulatory T-cell (Treg) expansion in vivo. Methods: We investigated the effect of iNKT stimulation by liposomal alpha-GC just after transplant on the subsequent immune reconstitution and the development of sclerodermatous cGVHD. Results: Our study showed that multiple administrations of liposomal alpha-GC modulated both host- and donor-derived iNKT cell homeostasis and induced an early expansion of donor Tregs. We also demonstrated that the immune modulation of the acute phase was followed by the decreased levels of CXCL13 in plasma and follicular helper T cells in lymph nodes, which inhibited germinal center formation, resulting in the efficient prevention of sclerodermatous cGVHD. Conclusions: These data demonstrated an important coordination of T- and B-cell immunity in the pathogenesis of cGVHD and may provide a novel clinical strategy for the induction of immune tolerance after allogeneic HSCT
