title: The earliest thymic progenitors for T cells possess myeloid lineage potential.
abstract: There exists controversy over the nature of haematopoietic progenitors of T cells. Most T cells develop in the thymus, but the lineage potential of thymus-colonizing progenitors is unknown. One approach to resolving this question is to determine the lineage potentials of the earliest thymic progenitors (ETPs). Previous work has shown that ETPs possess T and natural killer lymphoid potentials, and rare subsets of ETPs also possess B lymphoid potential, suggesting an origin from lymphoid-restricted progenitor cells. However, whether ETPs also possess myeloid potential is unknown. Here we show that nearly all ETPs in adult mice possess both T and myeloid potential in clonal assays. The existence of progenitors possessing T and myeloid potential within the thymus is incompatible with the current dominant model of haematopoiesis, in which T cells are proposed to arise from lymphoid-. Our results indicate that alternative models for lineage commitment during haematopoiesis must be considered.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
authors.forename: J Jeremiah
authors.initials: JJ
authors.lastname: Bell
authors.forename: Avinash
authors.initials: A
authors.lastname: Bhandoola
mesh_terms: D000818:Animals; D019070:Cell Lineage; D002478:Cells, Cultured; D018920:Coculture Techniques; D003713:Dendritic Cells / Q000166:cytology; D005260:Female; D006098:Granulocytes / Q000166:cytology; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000378:metabolism; D008264:Macrophages / Q000166:cytology; D051379:Mice; D008954:Models, Biological; D022423:Myeloid Cells / Q000166:cytology* / Q000378:metabolism; D017154:Stromal Cells / Q000166:cytology; D013601:T-Lymphocytes / Q000166:cytology* / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology*