The Journal of Immunology, Vol 143, Issue 11 3455-3460, Copyright © 1989 by American Association of Immunologists
Location of hemopoietic stem cells influences frequency of lymphoid engraftment in Xenopus embryos
JB Turpen and PB Smith
Department of Anatomy, University of Nebraska Medical Center, Omaha 68105.
The first hemopoietic stem cells to differentiate in Xenopus embryos arise
from ventral blood island (VBI) mesoderm. Progeny of these stem cells
contribute to larval E, macrophage, thymocyte, and B lymphocyte
populations. When small pieces of mesoderm are transplanted to a central
location within the VBI, the contribution of this mesoderm is predominantly
to erythropoiesis and engraftment of lymphoid populations is minimal. The
present experiments examined the influence of position within the VBI on
the contribution of single stem cells to lymphoid populations. Pieces of
diploid VBI mesoderm, containing an average of one hemopoietic stem cell,
were transplanted to either a central or a peripheral location within the
defined boundaries of the VBI of triploid, stage matched embryos. The
number of animals with donor- derived cells in lymphoid populations was
markedly increased when stem cells were grafted to a peripheral position.
In three cases, stem cells contributed to lymphoid populations at the
exclusion of erythroid populations. These data were consistent with the
notion of either a lymphoid stem cell or restricted B and T lymphocyte
precursors. These data also suggested that during embryogenesis, stochastic
differentiation of hemopoietic stem cells was influenced by regional
differences in the VBI microenvironment.
