title: Involvement of CCR9 at multiple stages of adult T lymphopoiesis.
abstract: The chemokine CCL25 is constitutively expressed in the thymus, and its receptor CCR9 is expressed on subsets of developing thymocytes. Nevertheless, the function of CCL25/CCR9 in adult thymopoiesis remains unclear. Here, we demonstrate that purified CCR9(-/-) hematopoietic stem cells are deficient in their ability to generate all major thymocyte subsets including double-negative 1 (DN1) cells in competitive transfers. CCR9(-/-) bone marrow contained normal numbers of lineage(-) Sca-1+c-kit+, common lymphoid progenitors, and lymphoid-primed multipotent progenitors (LMPP), and CCR9(-/-) LMPP showed similar T cell potential as their wild-type (WT) counterparts when cultured on OP9-delta-like 1 stromal cells. In contrast, early thymic progenitor and DN2 thymocyte numbers were reduced in the thymus of adult CCR9(-/-) mice. In fetal thymic organ cultures (FTOC), CCR9(-/-) DN1 cells were as efficient as WT DN1 cells in generating double-positive (DP) thymocytes; however, under competitive FTOC, CCR9(-/-) DP cell numbers were reduced significantly. Similarly, following intrathymic injection into sublethally irradiated recipients, CCR9(-/-) DN cells were out-competed by WT DN cells in generating DP thymocytes. Finally, in competitive reaggregation thymic organ cultures, CCR9(-/-) preselection DP thymocytes were disadvantaged significantly in their ability to generate CD4 single-positive (SP) thymocytes, a finding that correlated with a reduced ability to form TCR-MHC-dependent conjugates with thymic epithelial cells. Together, these results highlight a role for CCR9 at several stages of adult thymopoiesis: in hematopoietic progenitor seeding of the thymus, in the DN-DP thymocyte transition, and in the generation of CD4 SP thymocytes.
authors.affiliation: Immunolology Section, Lund University, BMCI13, Lund, Sweden.
authors.forename: Marcus
authors.initials: M
authors.lastname: Svensson
authors.forename: Jan
authors.initials: J
authors.lastname: Marsal
authors.forename: Heli
authors.initials: H
authors.lastname: Uronen-Hansson
authors.forename: Min
authors.initials: M
authors.lastname: Cheng
authors.forename: William
authors.initials: W
authors.lastname: Jenkinson
authors.forename: Corrado
authors.initials: C
authors.lastname: Cilio
authors.forename: Sten Eirik W
authors.initials: SE
authors.lastname: Jacobsen
authors.forename: Ewa
authors.initials: E
authors.lastname: Sitnicka
authors.forename: Graham
authors.initials: G
authors.lastname: Anderson
authors.forename: William W
authors.initials: WW
authors.lastname: Agace
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000276:immunology; D002454:Cell Differentiation / Q000276:immunology; D002478:Cells, Cultured; D006412:Hematopoietic Stem Cells / Q000276:immunology; D038041:Lymphopoiesis / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D054388:Receptors, CCR / Q000172:deficiency / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology
chemical_list: C119309:CC chemokine receptor 9; D054388:Receptors, CCR