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Age‐Related Changes in CCR9 + Circulating Lymphocytes: Are CCR9 + Naive T Cells Recent Thymic Emigrants?
Author(s) -
Olaussen R. W.,
Farstad I. N.,
Brandtzaeg P.,
Rugtveit J.
Publication year - 2001
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1046/j.1365-3083.2001.01008.x
Subject(s) - homing (biology) , biology , immunology , hematopoietic stem cell transplantation , chemokine receptor , stem cell , haematopoiesis , transplantation , immune system , chemokine , medicine , microbiology and biotechnology , ecology
The chemokine receptor CCR9 is reported to be predominantly expressed by thymocytes as well as by circulating gut‐homing and resident T cells in the small intestinal mucosa. Its ligand thymus‐expressed chemokine (TECK) is produced by thymic and small intestinal epithelium. Here we report that the proportion of circulating CCR9 + naive T cells (mostly CD4 + ) declines with age, from approximately 15% of all T cells at birth to around 1% in adults. The proportion of CCR9 + T cells lacking the classical gut‐homing receptor α4β7, was much higher in children than in adults. Therefore, circulating CD3 + CCR9 + CD45RA + cells have most likely left the thymus quite recently. This notion was supported by the small number of CCR9 + naive T cells which was present shortly after thymectomy. Establishing a phenotypic marker for recent thymic emigrants might provide a powerful tool in the clinical assessment and follow‐up after cancer chemotherapy, hematopoietic stem cell transplantation, and during antiretroviral treatment of human immunodeficiency virus (HIV)‐infected patients.