Clinical Research: Alternative DonorsEarly and Long-Term Impaired T Lymphocyte Immune Reconstitution after Cord Blood Transplantation with Antithymocyte Globulin

•We describe the different lymphocyte subsets kinetics (CD3+, CD4+, CD8+, CD19, and natural killer cells) after transplantation in umbilical cord blood recipients•We studied the predictive factors for each lymphocyte subset recovery after single umbilical cord blood transplantation in adult and pediatric patients•We report different factors that influenced lymphocyte subset recovery after cord blood transplantation: lower antithymocyte globulin dose, negative recipient cytomegalovirus serostatus, and younger patients•We describe the incidence and types of opportunistic infections in the different periods after cord blood transplantation•These results highlight the importance of optimizing the use of antithymocyte globulin in the conditioning regimen. Other factors, such as age and cytomegalovirus serostatus, also play a role that needs to be considered when designing new umbilical cord blood transplantation protocols to avoid infectious-related mortality

Immune reconstitution is crucial to the success of allogeneic hematopoietic stem cell transplantation. Umbilical cord blood transplantation (UCBT) has been associated with delayed immune reconstitution. We characterized the kinetics and investigated the risk variables affecting recovery of the main lymphocyte subsets in 225 consecutive pediatric and adult patients (males, n = 126; median age, 15; range, .3 to 60; interquartile range, 4 to 35) who underwent myeloablative single UCBT between 2005 and 2015 for malignant and nonmalignant disorders. Low CD4+ and CD8+ T cell counts were observed up to 12 months after UCBT. In contrast, B and natural killer cells recovered rapidly early after transplantation. In a multivariate regression model, factors favoring CD4+ T cell recovery ≥ 200 cells/µL were lower dose antithymocyte globulin (ATG) (hazard ratio [HR], 3.93; 95% confidence interval [CI], 2.3 to 5.83; P = .001), negative recipient cytomegalovirus (CMV) serostatus (HR, 3.76; 95% CI, 1.9 to 5.74; P = .001), and younger age (HR, 2.61; 95% CI, 1.01 to 3.47; P = .03). Factors favoring CD8+ T cell recovery ≥ 200 cells/µL were lower dose ATG (HR, 3.03; 95% CI, 1.4 to 5.1; P = .03) and negative recipient CMV serostatus (HR, 1.9; 95% CI, 1.63 to 2.15; P = .01). Our results demonstrate the significant negative impact of ATG on lymphocyte recovery. A reduction of the dose or omission of ATG could improve immune reconstitution and perhaps reduce opportunistic infections after UCBT.