Untangling the T branch of the hematopoiesis tree

Abstract

SummaryT cells develop in the thymus. Previous work suggested an early separation of lymphoid from myeloerythroid lineages during hematopoiesis, and hypothesized the thymus was settled exclusively by lymphoid-restricted hematopoietic progenitors. Recent data have instead established the existence of lymphoid-myeloid progenitors, which possess lymphoid and myeloid lineage potentials but lack erythroid potential. Myeloid and lymphoid potentials are present at the clonal level in early thymic progenitors, confirming that progenitors settling the thymus include lymphoid-myeloid progenitors. These results revise our view of the T lineage branch of hematopoiesis, and focus attention on the generation, circulation, and homing of lymphoid-myeloid progenitors to the thymus.

Somatic inactivation of Tp53 in hematopoietic stem cells or thymocytes predisposes mice to thymic lymphomas with clonal translocations

“…These cells proliferate and differentiate into pro-B or pro-T cells, respectively, which induce expression of the RAG1/RAG2 (RAG) endonuclease. 7,8 RAG catalyzes the assembly of TCR and Ig genes in G 1 phase cells through induction of DSBs at variable (V), diversity (D), and joining (J) gene segments. 9,10 Non-homologous end-joining (NHEJ) factors repair these DSBs to generate V(D)J coding joins that encode the first exons of TCR and Ig genes.…”

Identification of an NK/T cell–restricted progenitor in adult bone marrow contributing to bone marrow– and thymic-dependent NK cells

“…[1][2][3][4] This is of particular interest for the T-cell lineages, in which it remains unclear which stages of lineage restriction occur in the BM and subsequently in the thymus. [5][6][7] The recently identified lymphoid primed multipotent progenitor (LMPP), which lacks erythroid/megakaryocyte potentials but maintains combined lymphoid and granulocyte-monocyte potentials, 8 and the common lymphoid progenitor 9 represent lymphomyeloid and lymphoid-restricted candidate thymus seeding progenitors in adult BM. Both of these, however, are shared progenitors between the T-and B-cell lineages, of which the B-cell commitment is finalized in the BM, whereas the final stages of T-cell commitment are thought to take place predominantly or exclusively in the thymus.…”

Stem Cell Factor Consistently Improves Thymopoiesis after Experimental Transplantation of Murine or Human Hematopoietic Stem Cells in Immunodeficient Mice

“…LSK cells and the MPP (LSKflt3 + ) subset may develop into CLP1 and CLP2 that predominantly give rise to B cells and show low c-Kit expression (38). Of note, only the lymphoid-primed MPP and CLP subsets have been shown to efficiently seed the murine thymus (39)(40)(41).…”