title: Reduced-intensity conditioning regimen preserves thymic function in the early period after hematopoietic stem cell transplantation.
abstract: OBJECTIVE
  To compare T-cell reconstitution in two groups of patients submitted to allogeneic stem cell transplantation (SCT): those receiving reduced-intensity conditioning (RIC, n = 24) and those receiving myeloablative conditioning (MA, n = 27).
  
  
  METHODS
  Fifty-one consecutive patients undergoing SCT were evaluated. Serial assessments of lymphocyte subsets and T cell receptor excision circles (TRECs) levels were performed using multiparametric flow cytometry and real-time PCR, respectively.
  
  
  RESULTS
  During the first 6 months posttransplant, total and naïve CD4(+) T cell counts were higher after RIC-SCT than after MA-SCT (total CD4(+): p = 0.04, p = 0.08, and p = 0.058; naïve CD4(+): p = 0.14, p = 0.05, and p = 0.01 at 1, 3, and 6 months, respectively). In both groups of patients, TRECs levels were low or undetectable in the first 3 months after SCT and progressively increased during the study. However, a higher proportion of patients with detectable levels of TRECs was observed in RIC-SCT at 1 and 3 months and more patients in this group reached normal levels of TRECs at 6 months post-SCT. In the multivariate analysis, including factors such as type of donor (sibling vs unrelated), dose of CD34(+) cells infused with the graft, patient age, and graft-vs-host disease (GVHD), the most important factor influencing TRECs recovery in the early period after SCT was the type of conditioning regimen.
  
  
  CONCLUSIONS
  In this study, the pattern of immune reconstitution after RIC-SCT was different from that of MA-SCT and was characterized by higher posttransplant naïve CD4(+) T cell counts and TRECs levels in the early period after transplant.
authors.affiliation: Department of Hematology, Institute of Hematology and Oncology, Institut d'Investigacions Biomèdiques August Pi I Sunyer, IDIBAPS, Hospital Clínic, University of Barcelona, Barcelona, Spain.
authors.forename: Mónica
authors.initials: M
authors.lastname: Jiménez
authors.forename: Carmen
authors.initials: C
authors.lastname: Martínez
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Ercilla
authors.forename: Enric
authors.initials: E
authors.lastname: Carreras
authors.forename: Alvaro
authors.initials: A
authors.lastname: Urbano-Ispízua
authors.forename: Marta
authors.initials: M
authors.lastname: Aymerich
authors.forename: Neus
authors.initials: N
authors.lastname: Villamor
authors.forename: Nuria
authors.initials: N
authors.lastname: Amézaga
authors.forename: Montserrat
authors.initials: M
authors.lastname: Rovira
authors.forename: Francesc
authors.initials: F
authors.lastname: Fernández-Avilés
authors.forename: Anna
authors.initials: A
authors.lastname: Gaya
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Martino
authors.forename: Jorge
authors.initials: J
authors.lastname: Sierra
authors.forename: Emili
authors.initials: E
authors.lastname: Montserrat
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D018952:Antigens, CD34 / Q000276:immunology; D018791:CD4 Lymphocyte Count; D005260:Female; D006086:Graft vs Host Disease / Q000276:immunology; D006801:Humans; D008232:Lymphoproliferative Disorders / Q000276:immunology / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D020127:Recovery of Function / Q000276:immunology*; D033581:Stem Cell Transplantation; D016176:T-Lymphocyte Subsets / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D013950:Thymus Gland / Q000378:metabolism*; D019172:Transplantation Conditioning / Q000379:methods; D014184:Transplantation, Homologous
chemical_list: D018952:Antigens, CD34; D011948:Receptors, Antigen, T-Cell