title: Complex regulation of CCR9 at multiple discrete stages of T cell development.
abstract: We have conducted a comprehensive assessment of CCR9 expression and function at the important milestone stages of murine thymocyte development. We reveal an unusually complex regulatory pattern, in which CCR9 influences T cell development at several widely dispersed stages. We find that CCR9 is not expressed within the thymus until the double-negative (DN)3 stage, although it appears to contribute to T cell precursor development prior to residence in the thymus. CCR9 expression is influenced by pre-T cell receptor signals, and is dramatically up-regulated in a population that appears to be transitional between the DN4 and double-positive stages. In the periphery, functional CCR9 is expressed by all naive CD8 T cells, but not by naive CD4 T cells. To our knowledge, this latter finding is the first difference observed in homing receptor expression between naive lymphocyte populations. This suggests that naive CD8 T cells might have access to lymphoid microenvironments from which naive CD4 T cells are excluded.
authors.affiliation: Joint Program in Transfusion Medicine, Children's Hospital, Boston, MA 02115, USA. marc-andre.wurbel@childrens.harvard.edu
authors.forename: Marc-André
authors.initials: MA
authors.lastname: Wurbel
authors.forename: Bernard
authors.initials: B
authors.lastname: Malissen
authors.forename: James J
authors.initials: JJ
authors.lastname: Campbell
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D001854:Bone Marrow Cells / Q000276:immunology; D002454:Cell Differentiation / Q000276:immunology*; D002634:Chemotaxis, Leukocyte / Q000276:immunology; D005434:Flow Cytometry; D051379:Mice; D054388:Receptors, CCR; D019707:Receptors, Chemokine / Q000276:immunology* / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology / Q000254:growth & development* / Q000276:immunology
chemical_list: C119309:CC chemokine receptor 9; D054388:Receptors, CCR; D019707:Receptors, Chemokine