Immune reconstitution in patients with acquired severe aplastic anemia after haploidentical stem cell transplantation

Immune recovery (IR) after haploidentical stem cell transplantation (haplo-SCT) in severe aplastic anemia (SAA) patients remains relatively unknown. In this study, we examined immune cell subset counts and immunoglobulins in 81 SAA patients from day 30 to day 365 after haplo-SCT. Simultaneously, we determined which factors influence IR and analyzed the effects of immune cell subsets on transplant outcomes. We found that: (i) The reconstitution of different immune cell subsets occurred at different rates after haplo-SCT. Monocytes were the first to recover, followed by CD8+ T and CD19+ B cells, and finally CD4+ T cells. (ii) In the multivariate analysis, lower recipient age, female gender, high mononuclear cell counts in the graft and absence of CMV reactivation were associated with improved IR after transplant. (iii) A CD4/CD8 ratio less than 0.567 on day 30 post transplantation was associated with higher overall survival after haplo-SCT in SAA patients. In conclusion, SAA patients showed a faster recovery of monocytes and CD8+ T cells after haplo-SCT, whereas the recovery of the CD4+ T-cell subset was delayed. Our results may provide insight into methods for better predicting and modulating IR of SAA patients and subsequently improving outcomes after transplantation.