Demonstration that Thy(lo) subsets of mouse bone marrow that express high
levels of lineage markers are not significant hematopoietic progenitors
SJ Morrison, E Lagasse and IL Weissman
Department of Pathology, Stanford University School of Medicine, CA.
We have been unable to reproduce experiments suggesting the existence of
three lineage-restricted progenitor populations from mouse bone marrow.
Thy1.1loMac-1+B220+ cells were reported to give rise to greatly expanded
numbers of myeloid and lymphoid cells, while Thy1.1loMac- 1+B220- and
Thy1.1loMac-1-B220+ cells were reported to be highly proliferative myeloid
and B-lineage-restricted progenitors, respectively. Both Mac-1+ cell types
appear to be much less frequent than previously reported, and we observed
no activity consistent with their characterization as committed progenitors
of expanded numbers of cells. The original identification of these
populations may have resulted from a failure to distinguish bonafide
signals from autofluorescent background and nonspecific staining. The
progenitor activities originally associated with these populations may have
been due to hematopoietic stem cell contamination. This study shows that
low levels of Mac-1 are expressed on cells with multipotent progenitor
activity. Thy1.1loB220+Mac-1- cells can be purified from bone marrow, but
in these experiments they do not give rise to detectable levels of progeny
on injection into lethally irradiated mice. Thy1.1loB220+Mac-1- cells
appear to be pro-B cells without significant proliferation potential in
vivo. The finding that the described populations do not have the reported
progenitor activities leaves the pathways of stem cell differentiation open
to further study.
Volume 83,
Issue 12,
pp. 3480-3490,
06/15/1994
Copyright © 1994 by The American Society of Hematology
