The lymphocyte function of allogeneic peripheral blood stem cell grafts is associated with relapse and cytomegalovirus reactivation.
BACKGROUND Allogeneic hematopoietic stem cell transplantation (HSCT) is a treatment primarily for hematological malignancies. Infections, relapse, and graft versus host disease (GvHD) are some of the most common adverse events following HSCT. We aimed to evaluate whether the lymphocyte function of the stem cell graft was associated with these events. STUDY DESIGN AND METHODS We included peripheral blood stem cell (PBSC) grafts from 53 donors to HSCT recipients. The grafts' lymphocyte function was assessed by in vitro blast formation, expression of activation markers, and cytokine production upon stimulation. The cellular composition of the grafts was determined with flow cytometry. Results were compared with the incidence of infections, GvHD, relapse, and survival in the HSCT recipients. RESULTS We found an association between lower graft T cell response upon mitogen or superantigen stimulation and cytomegalovirus reactivation (p = .013 and p = .0028). Recipients of grafts with an above-median programmed death-1 (PD-1) expression on CD8+ T cell blasts had a higher incidence of relapse and lower overall survival (p = .02). Both findings remained significant in the multivariable analysis. DISCUSSION Measurement of the lymphocyte response upon mitogen stimulation of PBSC grafts might provide beneficial knowledge of graft-related factors that contribute to the incidence of complications after HSCT.