Pre-transplantation thymic function is associated with the risk of acute graft versus host disease and cytomegalovirus viremia after allogeneic hematopoietic stem cell transplantation

<b>Objectives:</b> To analyze the kinetics of T-cell subsets and thymic function reconstitution after allogeneic hematopoietic stem cell transplantation (AHSCT); to determine whether sjTREC (signal joint TCR rearrangement excision circle) and CD31-positive recent thymic emigrant (CD31 + RTE) are correlated with acute graft versus host disease (aGVHD) or CMV (cytomegalovirus) viremia after AHSCT. <b>Methods:</b> Forty-nine patients who underwent AHSCT in our institution were prospectively enrolled. Periphery blood samples were collected before conditioning and at 1, 2, 3 months after AHSCT. T-cell subsets were analyzed with flow cytometry. Genomic DNA was purified from peripheral blood mononuclear cells (PBMCs), and sjTREC was quantified by real-time PCR. Impact of sjTREC and CD31 + RTE on aGVHD and CMV viremia was evaluated by univariate and multivariate Cox regression analyses. <b>Results:</b> The analyzed T-cell subsets and sjTREC of patients before AHSCT were all significantly lower than those of healthy donors (<i>p</i> &lt; 0.05). sjTREC and CD31 + RTE were remarkably decreased in 3 months after AHSCT (<i>p</i> &lt; 0.05). Patients with lower pre-transplantation sjTREC and CD31 + RTE level had higher incidence of CMV viremia after AHSCT (<i>p</i> &lt; 0.05). sjTREC/10⁶ PBMCs was negatively correlated with aGVHD (<i>p</i> = 0.024). <b>Conclusion:</b> Thymic function was impaired before transplantation, and was consistently decreased in 3 months after AHSCT. Patients who had lower pre-transplantation sjTREC level were at high risk of aGVHD and CMV viremia after AHSCT, low pre-transplantation CD31 + RTE was correlated with CMV viremia after AHSCT.