title: Evaluation of thymopoiesis using T cell receptor excision circles (TRECs): differential correlation between adult and pediatric TRECs and naïve phenotypes.
abstract: To determine whether the thymus is still functional despite age-related involution, we measured a biomarker for thymopoiesis known as the T cell receptor excision circle (TREC) from peripheral blood mononuclear cells (PBMCs) of 148 healthy children and from PBMCs, CD4(+), and CD8(+) cells of 32, 30, and 50 healthy adults, respectively. We demonstrate that during the first 5 years of life, thymic output is decreased (P 0.002) but not dramatically (r = -0. 282). Among adults aged 23-58, thymic output was inversely correlated with age, as measured from PBMCs (r = -0.628, P < 0.0005), CD4(+) (r = -0.530, P 0.003), and CD8(+) fractions (r = -0.385, P 0. 006). A strong correlation existed between pediatric PBMC TRECs and the expression of three naïve phenotypic markers (CD45RA(+)CD45RO(-), CD45RA(+)CD62L(+), and CD45RO(-)CD27(+)CD95(low)). Adult PBMC TRECs correlated only with the expression of CD45RA(+)CD45RO(-) (r = 0.459, P 0.012). Our data suggest that in adults CD45RA(+)CD45RO(-) may be enriched for TRECs and add to a growing body of evidence illustrating intact thymic function in adulthood.
authors.affiliation: Department of Immunology/Microbiology, Rush-Presbyterian- St. Luke's Medical Center, Chicago, Illinois 60612, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Steffens
authors.forename: L
authors.initials: L
authors.lastname: Al-Harthi
authors.forename: S
authors.initials: S
authors.lastname: Shott
authors.forename: R
authors.initials: R
authors.lastname: Yogev
authors.forename: A
authors.initials: A
authors.lastname: Landay
mesh_terms: D000293:Adolescent; D000328:Adult; D015496:CD4-Positive T-Lymphocytes / Q000737:chemistry; D018414:CD8-Positive T-Lymphocytes / Q000737:chemistry; D002455:Cell Division; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D015329:Gene Rearrangement, T-Lymphocyte; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007963:Leukocytes, Mononuclear / Q000737:chemistry; D011948:Receptors, Antigen, T-Cell / Q000097:blood / Q000235:genetics; D013950:Thymus Gland / Q000166:cytology*
chemical_list: D011948:Receptors, Antigen, T-Cell