RIKEN Press R ele ase |
April 1 0, 2008 |
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A clte relationship between T cells and phagocytes
establishing a new paradigm in hematopo | |||
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Scientists in the RIKEN Research Center for Allergy and Immunology have recently made a discovery that disproves a widely believed model for the process of hematopoiesis and, instead, proposes a novel model. They have revealed that T cell progenitors in the adult thymus produce not only T lymphocytes, but also macrophages, phagocytic cells that belong to myeloid lineage. This work was done by Hiroshi Kawamoto, a team leader of Laboratory for Lymphocyte Development, together with his colleagues including Haruka Wada, a research scientist, and Yoshimoto Katsura, a visiting scientist of the research team. This work will be published in Nature (April, 10). During hematopoiesis, pluripotent hematopoietic stem cells are sequentially restricted to give rise to a variety of lineage committed progenitors. The classical model of hematopoiesis postulates that in the first step of differentiation, the hematopoietic stem cell generates common myelo-erythroid progenitors and common lymphoid progenitors (CLPs) (Figure 1A). By using a clonal analysis of lympho-hematopoietic cells present in the fetal liver of mice, however, the research team has previously demonstrated that myeloid potential is maintained even as the lineage branches segregate towards T and B cells. The team has therefore proposed the "myeloid-based" model of hematopoiesis, where the stem cell initially generates common myelo-erythroid progenitors and common myelo-lymphoid progenitors (Figure 1B). T and B cell progenitors subsequently arise from common myelo-lymphoid progenitors through myeloid-T and myeloid-B stages, respectively. By contrast, I. Weissman's group in Stanford University (USA) previously reported that CLPs are present in a bone marrow subpopulation in the adult mouse. In order to reconcile these disparate findings between fetal liver and adult bone marrow, the concept has emerged that fetal and adult hematopoiesis differ, with the CLP stage existing only during adult hematopoiesis.
These findings therefore argue against the classical dichotomy model, in which T cells are derived from CLPs and, instead, support the validity of the myeloid-based model in both adult and fetal hematopoiesis. |
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| RIKEN, one of Japan's leading research institutes, conducts basic and applied experimental research in a wide range of science and technology fields including physics, chemistry, medical science, biology and engineering. Initially established as a private research foundation in Tokyo in 1917, RIKEN became an independent administrative institution in 2003. For more information, visit www.riken.jp | |||
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