title: Efforts of the human immune system to maintain the peripheral CD8+ T cell compartment after childhood thymectomy.
abstract: BACKGROUND
  Homeostatic mechanisms to maintain the T cell compartment diversity indicate an ongoing process of thymic activity and peripheral T cell renewal during human life. These processes are expected to be accelerated after childhood thymectomy and by the influence of cytomegalovirus (CMV) inducing a prematurely aged immune system. The study aimed to investigate proportional changes and replicative history of CD8+ T cells, of recent thymic emigrants (RTEs) and CD103+ T cells (mostly gut-experienced) and the role of Interleukin-(IL)-7 and IL-7 receptor (CD127)-expressing T cells in thymectomized patients compared to young and old healthy controls.
  
  
  RESULTS
  Decreased proportions of naive and CD31 + CD8+ T cells were demonstrated after thymectomy, with higher proliferative activity of CD127-expressing T cells and significantly shorter relative telomere lengths (RTLs) and lower T cell receptor excision circles (TRECs). Increased circulating CD103+ T cells and a skewed T cell receptor (TCR) repertoire were found after thymectomy similar to elderly persons. Naive T cells were influenced by age at thymectomy and further decreased by CMV.
  
  
  CONCLUSIONS
  After childhood thymectomy, the immune system demonstrated constant efforts of the peripheral CD8+ T cell compartment to maintain homeostasis. Supposedly it tries to fill the void of RTEs by peripheral T cell proliferation, by at least partly IL-7-mediated mechanisms and by proportional increase of circulating CD103+ T cells, reminiscent of immune aging in elderly. Although other findings were less significant compared to healthy elderly, early thymectomy demonstrated immunological alterations of CD8+ T cells which mimic features of premature immunosenescence in humans.
authors.affiliation: Department of Pediatrics, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Manuela
authors.initials: M
authors.lastname: Zlamy
authors.affiliation: Department of Pediatrics, University Hospital Wuerzburg, University of Wuerzburg, Josef-Schneider-Str. 2, 97080 Wuerzburg, Germany.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Almanzar
authors.affiliation: Institute of Legal Medicine, Medical University Innsbruck, Innsbruck, Austria ; Penn State Eberly College of Science, University Park, PA USA.
authors.forename: Walther
authors.initials: W
authors.lastname: Parson
authors.affiliation: Department of Haematology and Oncology, University of Greifswald, Greifswald, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schmidt
authors.affiliation: Department of Internal Medicine, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Leierer
authors.affiliation: Institute for Biomedical Aging Research, University of Innsbruck, Innsbruck, Austria.
authors.forename: Birgit
authors.initials: B
authors.lastname: Weinberger
authors.affiliation: Department of Pediatrics, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Verena
authors.initials: V
authors.lastname: Jeller
authors.affiliation: Department of Radiology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Karin
authors.initials: K
authors.lastname: Unsinn
authors.affiliation: Department of Pediatrics, University Hospital Wuerzburg, University of Wuerzburg, Josef-Schneider-Str. 2, 97080 Wuerzburg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Eyrich
authors.affiliation: Department of Hygiene and Medical Microbiology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Würzner
authors.affiliation: Department of Pediatrics, University Hospital Wuerzburg, University of Wuerzburg, Josef-Schneider-Str. 2, 97080 Wuerzburg, Germany.
authors.forename: Martina
authors.initials: M
authors.lastname: Prelog
keywords: CD8; CMV; Naive T cells; TCR diversity; TRECs; Telomeres; Thymectomy
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