Influence of post-transplant mucosal-associated invariant T cell recovery on the development of acute graft-versus-host disease in allogeneic bone marrow transplantation.

Mucosal-associated invariant T (MAIT) and invariant natural killer T (iNKT) cells are T cell subpopulations that possess innate-like properties. We examined the impact of post-hematopoietic stem cell transplantation (HSCT) MAIT and iNKT cell recovery on the clinical outcomes of 69 patients who underwent allogeneic HSCT at Kyoto University Hospital. Multivariate analyses identified the absolute number of MAIT cells (< 0.48/µL on day 60 post-HSCT) as the sole independent risk factor for grade I-IV and grade II-IV acute graft-versus-host disease (aGVHD) among patients who underwent bone marrow transplantation; no correlation was observed between post-HSCT iNKT cell recovery and the development of aGVHD. Six of the 15 patients in the MAIThigh (≥ 0.48/µL) group developed aGVHD, five within the first 30 days post HSCT. In contrast, 13 of the 15 patients in the MAITlow (< 0.48/µL) group developed aGVHD, seven after day 30 post HSCT. The overall survival of the MAITlow group was slightly shorter than that of the MAIThigh group. Thus, the post-HSCT recovery of MAIT cells is closely related to the development of delayed onset aGVHD and the outcome of post-HSCT, suggesting its utility for identifying a subset of patients that requires more prolonged and/or intense GVHD prophylaxis.