Characteristics of early murine B-lymphocyte precursors and their direct sensitivity to negative regulators.
Recently, a collection of surface markers was exploited to isolate viable Lin(-) TdT(+) cells from murine bone marrow. These early pro-B cells were enriched for B-lineage lymphocyte precursor activity measured by short-term culture and had little responsiveness to myeloid growth factors. Early precursors can be propagated with remarkably high cloning frequencies in stromal cell-free, serum-free cultures, permitting this analysis of direct regulatory factors. Expression of the interleukin-7 receptor (IL-7Ralpha) chain marks functional precursors and IL-7 is necessary for progression beyond the CD45RA(+) CD19(-) stage. Efficient survival and differentiation were only observed when stem cell factor and Flt-3 ligand were also present. IL-7-responsive CD19(+) precursors are estrogen resistant. However, B-lineage differentiation was selectively abrogated when highly purified Lin(-) precursors were treated with hormone in the absence of stromal cells. In addition, early stages of B lymphopoiesis were arrested by limitin, a new interferon (IFN)-like cytokine as well as IFN-alpha, IFN-gamma, or transforming growth factor beta (TGF-beta), but not by epidermal growth factor (EGF). Lin(-) TdT(+) early pro-B cells are shown here to be CD27(+) AA4.1(+/-)Ki-67(+) Ly-6C(-) Ly-6A/Sca-1(Lo/-)Thy-1(-)CD43(+) CD4(+/-)CD16/32(Lo/-)CD44(Hi) and similar in some respects to the "common lymphoid progenitors" (CLP) identified by others. Although early pro-B cells have lost myeloid differentiation potential, transplantation experiments described here reveal that at least some can generate T lymphocytes. Of particular importance is the demonstration that a pivotal early stage of lymphopoiesis is directly sensitive to negative regulation by hormones and cytokines.
Kouro
T
T
Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA.
Medina
K L
KL
Oritani
K
K
Kincade
P W
PW
D000818:Animals; D015703:Antigens, CD / Q000502:physiology; D001402:B-Lymphocytes / Q000166:cytology* / Q000502:physiology; D002454:Cell Differentiation; D019070:Cell Lineage / Q000502:physiology; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000502:physiology; D015851:Interleukin-7 / Q000502:physiology; D008565:Membrane Proteins; D051379:Mice; D008807:Mice, Inbred BALB C; D020395:Receptors, Interleukin-7 / Q000502:physiology
D015703:Antigens, CD; D015851:Interleukin-7; D008565:Membrane Proteins; D020395:Receptors, Interleukin-7; C084881:flt3 ligand protein