title: Characterization of human CD25+ CD4+ T cells in thymus, cord and adult blood.
abstract: CD4(+) CD25(+) regulatory T cells prevent organ-specific autoimmune diseases in various animal models. We analysed human lymphoid tissues to identify similar CD25(+) regulatory T cells. Adult peripheral blood contained two populations of CD4(+) T cells that expressed CD25 at different densities. The larger population (approximately 40%) expressed intermediate levels of CD25 (CD25(+)) and displayed a memory T-cell phenotype (CD45RA-/RO(+), CD45RB(low), CD95(+), CD62L(low), CD38(low)). The smaller population of cells (approximately 2%) expressed very high levels of CD25 (CD25(++)). In addition to the activation/memory T-cell antigens mentioned above they also expressed intracellular CD152 (CTLA-4) as well as enhanced levels of cell-surface CD122, similar to the murine CD4(+) CD25(+) regulatory counterpart. To exclude that the CD25(++) cells had not been recently primed by external antigen we analysed cord blood and thymus. CD25(++), CD152(+) and CD122(++) cells were present in paediatric thymus (10% of CD4(+) CD8(-) thymocytes) expressing signs of recent selection (CD69+) and in cord blood (5% of CD4(+) cells) where they showed a naive phenotype. In addition, cord blood contained a small population of CD25(+) cells (approximately 2% of CD4 T cells) that were CD152(-) and CD122(low) and displayed signs of activation. Together with published data that CD25(+) CD25(++) cells from the thymus and peripheral blood are regulatory, our results suggest that regulatory CD25(+) T cells leave the thymus in a naïve state and become activated in the periphery.
authors.affiliation: Department of Rheumatology, Göteborg University, Göteborg, Sweden.
authors.forename: Kajsa
authors.initials: K
authors.lastname: Wing
authors.forename: Ann
authors.initials: A
authors.lastname: Ekmark
authors.forename: Helen
authors.initials: H
authors.lastname: Karlsson
authors.forename: Anna
authors.initials: A
authors.lastname: Rudin
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Suri-Payer
mesh_terms: D000328:Adult; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology; D002478:Cells, Cultured; D005312:Fetal Blood / Q000276:immunology*; D006801:Humans; D016130:Immunophenotyping; D007231:Infant, Newborn; D008213:Lymphocyte Activation / Q000276:immunology; D008875:Middle Aged; D015375:Receptors, Interleukin-2 / Q000032:analysis* / Q000097:blood; D016176:T-Lymphocyte Subsets / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology*
chemical_list: D015375:Receptors, Interleukin-2