title: Factors influencing lymphocyte reconstitution after allogeneic hematopoietic stem cell transplantation in children.
abstract: BACKGROUND
  Immune reconstitution (IR) after hematopoietic stem cell transplantation (HSCT) reduces transplantation-related complications such as infection and improves HSCT outcomes.
  
  
  METHODS
  We retrospectively analyzed IR of lymphocyte subpopulations in 38 pediatric patients for hematologic malignant diseases after allogeneic HSCT from April 2006 to July 2008. T-cell-, B-cell-, and natural killer (NK) cell-associated antigens were assayed in peripheral blood by flow cytometry analysis of 5 lymphocyte subsets, CD3+, CD3+/CD4+, CD4+/CD8+, CD16+/CD56+, and CD19+, before and 3 and 12 months after transplantation.
  
  
  RESULTS
  Reconstitutions of CD16+/CD56+ and CD3+/CD8+ lymphocytes were achieved rapidly, whereas that of CD3+/CD19+ lymphocytes occurred later. Age was not related to reconstitution of any lymphocyte subset. Total body irradiation (TBI) and anti-thymocyte globulin (ATG) administration were related to delayed reconstitution of total lymphocytes and CD3+ lymphocytes, respectively. Reconstitutions of CD3+/CD4+ lymphocytes and CD3+/CD8+ lymphocytes were significantly delayed in patients who received umbilical cord blood stem cells. In patients with chronic graft-versus-host disease (cGVHD), recovery of the total lymphocyte count and CD19+ lymphocytes at 3 months post-transplant were significantly delayed. However, acute GVHD (aGVHD) and cytomegalovirus (CMV) reactivation did not influence the IR of any lymphocyte subset. Further, delayed reconstitution of lymphocyte subsets did not correspond to inferior survival outcomes in this study.
  
  
  CONCLUSIONS
  We observed that some lymphocyte reconstitutions after HSCT were influenced by the stem cell source and preparative regimens. However, delayed CD19+ lymphocyte reconstitution may be associated with cGVHD.
authors.affiliation: Division of Pediatric Hematology/Oncology, Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Keun Wook
authors.initials: KW
authors.lastname: Bae
authors.forename: Bo Eun
authors.initials: BE
authors.lastname: Kim
authors.forename: Kyung Nam
authors.initials: KN
authors.lastname: Koh
authors.forename: Ho Joon
authors.initials: HJ
authors.lastname: Im
authors.forename: Jong Jin
authors.initials: JJ
authors.lastname: Seo