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A study conducted presents an evidence for a population of cells, which although sustaining a high proliferative and combined lympho-myeloid differentiation potential, have lost the ability to adopt erythroid and megakaryocyte lineage fates. It is shown that cells in the Lin(super -1)Sca-1(super +1)-kit(super +1) hematopoietic stem cell (HSC) compartment coexpressing high levels of the tyrosine kinase receptor Flt3 sustains granulocyte, monocyte, and B and T cell potentials.

All blood cell lineages derive from a common hematopoietic stem cell (HSC). The current model implicates that the first lineage commitment step of adult pluripotent HSCs results in a strict separation into common lymphoid and common myeloid precursors. We present evidence for a population of cells which, ala though sustaining a high proliferative and combined lympho-myeloid differentiation potential, have lost the ability to adopt erythroid and megakaryocyte lineage fates. Cells in the Lin-Sca-1+c-kit+ HSC compartment co-expressing high levels of the tyrosine kinase receptor Fit3- sustain granulocyte, monocyte, and B and T cell potentials but in contrast to Lin-Sca-1+c-kit+Fit3- HSCs fail to produce significant erythroid and megakaryocytic progeny. This distinct lineage restriction site is accompanied by down regulation of genes for regulators of erythroid and megakaryocyte development. In agreement with representing a lymphoid primed progenitor, Lit-Sca-1+c-kit+CD34+Fit3- cells display upregulated IL-7 receptor gene expression. Based on these observations, we propose a revised road map for adult blood lineage development. [ABSTRACT FROM AUTHOR]