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Abstract Background The immune reconstitution after allogeneic hematopoietic stem cell transplantation (allo‐HSCT) is crucial for preventing infections and relapse and enhancing graft‐versus‐tumor effects. B cells play an important role in humoral immunity and immune regulation, but their reconstitution after allo‐HSCT has not been well studied. Methods In this study, we analyzed the dynamics of B cells in 252 patients who underwent allo‐HSCT for 2 years and assessed the impact of factors on B‐cell reconstitution and their correlations with survival outcomes, as well as the development stages of B cells in the bone marrow and the subsets in the peripheral blood. Results We found that the B‐cell reconstitution in the bone marrow was consistent with the peripheral blood ( p = 0.232). B‐cell reconstitution was delayed by the male gender, age >50, older donor age, the occurrence of chronic and acute graft‐versus‐host disease, and the infections of fungi and cytomegalovirus. The survival analysis revealed that patients with lower B cells had higher risks of death and relapse. More importantly, we used propensity score matching to obtain the conclusion that post‐1‐year B‐cell reconstitution is better in females. Meanwhile, using mediation analysis, we proposed the age‐B cells‐survival axis and found that B‐cell reconstitution at month 12 posttransplant mediated the effect of age on patient survival ( p = 0.013). We also found that younger patients showed more immature B cells in the bone marrow after transplantation ( p = 0.037). Conclusion Our findings provide valuable insights for optimizing the management of B‐cell reconstitution and improving the efficacy and safety of allo‐HSCT.
Zhou et al. (Mon,) studied this question.