title: Selective thymus settling regulated by cytokine and chemokine receptors.
abstract: To generate T cells throughout adult life, the thymus must import hemopoietic progenitors from the bone marrow via the blood. In this study, we establish that thymus settling is selective. Using nonirradiated recipient mice, we found that hemopoietic stem cells were excluded from the thymus, whereas downstream multipotent progenitors (MPP) and common lymphoid progenitors rapidly generated T cells following i.v. transfer. This cellular specificity correlated with the expression of the chemokine receptor CCR9 by a subset of MPP and common lymphoid progenitors but not hemopoietic stem cells. Furthermore, CCR9 expression was required for efficient thymus settling. Finally, we demonstrate that a prethymic signal through the cytokine receptor fms-like tyrosine kinase receptor-3 was required for the generation of CCR9-expressing early lymphoid progenitors, which were the most efficient progenitors of T cells within the MPP population. We conclude that fms-like tyrosine kinase receptor-3 signaling is required for the generation of T lineage-competent progenitors, which selectively express molecules, including CCR9, that allow them to settle within the thymus.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Schwarz
authors.forename: Arivazhagan
authors.initials: A
authors.lastname: Sambandam
authors.forename: Ivan
authors.initials: I
authors.lastname: Maillard
authors.forename: Benjamin C
authors.initials: BC
authors.lastname: Harman
authors.forename: Paul E
authors.initials: PE
authors.lastname: Love
authors.forename: Avinash
authors.initials: A
authors.lastname: Bhandoola
mesh_terms: D000818:Animals; D016026:Bone Marrow Transplantation; D002454:Cell Differentiation / Q000276:immunology*; D002465:Cell Movement / Q000276:immunology; D016207:Cytokines / Q000276:immunology*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology; D051379:Mice; D039902:Multipotent Stem Cells / Q000166:cytology / Q000276:immunology; D054388:Receptors, CCR; D019707:Receptors, Chemokine / Q000276:immunology*; D015398:Signal Transduction / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology*; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000276:immunology*; D014916:Whole-Body Irradiation
chemical_list: C119309:CC chemokine receptor 9; D016207:Cytokines; D054388:Receptors, CCR; D019707:Receptors, Chemokine; D040281:Vascular Endothelial Growth Factor Receptor-1