(Philadelphia) — T cells are critically important for human immunological defenses against pathogens, yet little is known about their early development. T cells are made in the thymus, but ultimately come from hematopoietic stem cells in the bone marrow, from which all blood-cell types begin. A progenitor cell must leave the bone marrow to seed the thymus, eventually giving rise to T cells. The identity of this cell has long been sought and might help correct disorders of T-cell production, says Avinash Bhandoola, MD, PhD, Assistant Professor of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine.

Bhandoola and Benjamin Schwarz, a fifth year MD/PhD student, identified such a cell. "Our work really provides the tools," says Bhandoola. "Everyone can now study this cell, and a better understanding of early steps in T-cell development should follow." They describe their findings in the current advance online publication of Nature Immunology.

Hematopoietic stem cells (HSCs) are the ultimate progenitors of all blood cell types, from platelets and red blood cells (erythrocytes) to immune cells like T cells and B cells. But T-cell development differs from other cell lineages in that it occurs in the thymus, a small organ situated under the breastbone near the heart, rather than the bone marrow. To do this, though, the thymus periodically imports marrow T-cell progenitor cells via the circulatory system. The cell types that travel from the marrow to the thymus were not exclusively pinned down, but researchers have suggested HSCs themselves, multipotent progenitor (MPPs) cells, or a common lymphoid progenitor (CLP) cell from the marrow itself, as possible candidates.

In a previous study, Bhandoola along with David Allman, PhD, an Assistant Professor in Penn's Department of Pathology and Laboratory Medicine, identified the earliest T-lineage progenitor in the thymus and demonstrated that it was n
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Contact: Karen Kreeger
karen.kreeger@uphs.upenn.edu
215-349-5658
University of Pennsylvania School of Medicine
5-Aug-2004

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