PHILADELPHIA â€“ Scientists at the University of Pennsylvania
School of Veterinary Medicine have found a new wrinkle in the
developmental biology dogma that cell differentiation occurs
irreversibly as stem cells give rise to increasingly specialized
types of offspring cells. The researchers have shown that
certain mouse cells retain an ability to oscillate between very
distinct blood cell types â€“ B-cells and macrophages â€“ long
after what has been commonly regarded as the point of no return.
These latest findings on the phenomenon sometimes referred to as
"lineage promiscuity" appear on the Web site of the journal
Blood and will be published in the journal's print edition in
March 2003. "This work reveals that seemingly committed cells
have more plasticity than we had thought," said senior author
Andrei Thomas-Tikhonenko, assistant professor of pathobiology at
Penn. "It appears there is at least a small window where
terminally differentiated cells vacillate on which identity to
adopt. We suspect that this