CD34-positive early stages of human T-cell differentiation.
Thymus, the main organ for T lymphopoiesis, requires a permanent influx of progenitors from bone marrow (BM) or fetal liver. An essential question relating to early T-cell development is the identification of the progenitor population which actually homes to the thymus. Recent findings have shown that human multipotent progenitor/stem cells expressing CD34 have the capacity to differentiate into T cells when introduced into a thymic environment. More mature CD34+ bone marrow cells coexpressing CD7 and having a poor myeloid differentiation capacity can also efficiently differentiate into T cells in vitro. These lymphoid committed precursors might be the true thymic repopulating cells. In the thymus, cells with a similar CD34+7+ phenotype include the most primitive thymocyte precursors. CD34+ thymocytes have no myeloid differentiation potential, but may include precursors for natural killer (NK) cells. Interleukin-7 (IL7) is a potent in vitro growth factor for CD34+ thymocytes. Whereas current data do not support a crucial role for IL2, patients with IL2 receptor gamma chain (IL2R gamma) deficiency lack T- and NK cells. The recent demonstration that IL2R gamma is part of the receptor for IL7 strongly suggests that this cytokine plays an essential role in in vivo T lymphocyte and NK development.
Schmitt
C
C
CNRS URA625, Hôpital de la Pitié-Salpétrière, Paris, France.
Ktorza
S
S
Sarun
S
S
Verpilleux
M P
MP
Blanc
C
C
Deugnier
M A
MA
Dalloul
A
A
Debré
P
P
D000818:Animals; D015703:Antigens, CD / Q000502:physiology*; D018952:Antigens, CD34; D002454:Cell Differentiation / Q000502:physiology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000502:physiology; D006801:Humans; D013601:T-Lymphocytes / Q000166:cytology*; D013950:Thymus Gland / Q000166:cytology
D015703:Antigens, CD; D018952:Antigens, CD34