title: The stream of precursors that colonizes the thymus proceeds selectively through the early T lineage precursor stage of T cell development.
abstract: T cell development in the thymus depends on continuous colonization by hematopoietic precursors. Several distinct T cell precursors have been identified, but whether one or several independent precursor cell types maintain thymopoiesis is unclear. We have used thymus transplantation and an inducible lineage-tracing system to identify the intrathymic precursor cells among previously described thymus-homing progenitors that give rise to the T cell lineage in the thymus. Extrathymic precursors were not investigated in these studies. Both approaches show that the stream of T cell lineage precursor cells, when entering the thymus, selectively passes through the early T lineage precursor (ETP) stage. Immigrating precursor cells do not exhibit characteristics of double-negative (DN) 1c, DN1d, or DN1e stages, or of populations containing the common lymphoid precursor 2 (CLP-2) or the thymic equivalent of circulating T cell progenitors (CTPs). It remains possible that an unknown hematopoietic precursor cell or previously described extrathymic precursors with a CLP, CLP-2, or CTP phenotype feed into T cell development by circumventing known intrathymic T cell lineage progenitor cells. However, it is clear that of the known intrathymic precursors, only the ETP population contributes significant numbers of T lineage precursors to T cell development.
authors.affiliation: Department of Developmental Immunology, Max-Planck-Institute of Immunobiology, 79108 Freiburg, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Benz
authors.forename: Vera C
authors.initials: VC
authors.lastname: Martins
authors.forename: Freddy
authors.initials: F
authors.lastname: Radtke
authors.forename: Conrad C
authors.initials: CC
authors.lastname: Bleul
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D019070:Cell Lineage; D005434:Flow Cytometry; D017353:Gene Deletion; D008213:Lymphocyte Activation; D051379:Mice; D051881:Receptor, Notch1 / Q000172:deficiency; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013370:Subrenal Capsule Assay; D013601:T-Lymphocytes / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology* / Q000637:transplantation
chemical_list: C497762:Notch1 protein, mouse; D051881:Receptor, Notch1