title: Immune reconstitution after hematopoietic cell transplantation.
abstract: OBJECTIVE
  Successful immune reconstitution is important for decreasing posthematopoietic cell transplant (post-HCT) infections, relapse, and secondary malignancy, without increasing graft-versus-host disease (GVHD). Here we review how different parts of the immune system recover, and the relationship between recovery and clinical outcomes.
  
  
  RESULTS
  Innate immunity (e.g., neutrophils, natural killer cells) recovers within weeks, whereas adaptive immunity (B and T cells) recovers within months to years. This has been known for years; however, more recently, the pattern of recovery of additional immune cell subsets has been described. The role of these subsets in transplant complications like infections, GVHD and relapse is becoming increasingly recognized, as gleaned from studies of the association between subset counts or function and complications/outcomes, and from studies depleting or adoptively transferring various subsets.
  
  
  CONCLUSIONS
  Lessons learned from observational studies on immune reconstitution are leading to new strategies to prevent or treat posttransplant infections. Additional knowledge is needed to develop effective strategies to prevent or treat relapse, second malignancies and GVHD.
authors.affiliation: University of Calgary/Alberta Health Services, Calgary, Alberta, Canada.
authors.forename: Mark
authors.initials: M
authors.lastname: Bosch
authors.forename: Faisal M
authors.initials: FM
authors.lastname: Khan
authors.forename: Jan
authors.initials: J
authors.lastname: Storek
mesh_terms: D056704:Adaptive Immunity; D000941:Antigens / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D007113:Immunity, Innate; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000941:Antigens