Abstract
In humans, little is known about post-natal lymphoid progenitors, especially those able to circulate, colonize the thymus and generate T lymphocytes. On the basis of a previous work published by Anne Galy in 1995, we have detected in the human post-natal bone marrow up to 60 yrs of age a population of progenitors characterized by their CD34+Lin-CD10+ phenotype. Their differentiation potential analysed by culture in methylcellulose medium indicated that in contrast with their CD10− counterparts, CD10+ progenitors have lost erythroid and myeloid potential. On the other hand, CD10+ progenitors cultured on MS5 or OP9/hDL1 stroma demonstrated an enriched capacity to generate B, T and NK lymphocytes as compared to CD10− precursors. In limiting dilution assays, the high lymhoid potential of CD10+ population was confirmed, since 1 out 15 of them gave rise to T cells, 1 out 23 to B cells and 1 out 90 to NK cells. Gene expression profile shows that CD10+ cells express both B and T restricted factors, such as RAG, Gata3, Pax 5 and TdT. In addition, recombination at the IgH locus is already going on, with multiple DJ, but also VDJ recombination products detected. More importantly, CD10+ precursors circulate in the peripheral blood and are detected in the thymus where they are part of the most immature thymocytes CD34+CD1a-CD38-. Altogether, our results demonstrate for the first time the existence of a post-natal lymphoid progenitor population with a broad lymphoid potential and the ability to reach the thymus and generate efficiently T cells. On the long term, their full characterization will pave the way for their enrichment and usage in therapy of primary lymphoid immunodeficiencies.
Limiting dilution comparison of the repertoires of high and low responder MHC-restricted T cells.