“This really shows that elements, that chemistry, is in control of
biology in a way we haven’t thought about.” — TERESA WOODRUFF
cells fail a test
By Tina Hesman Saey
Stem cells made by reprogramming
adult cells from a patient’s own body can
come under attack by the immune system, a new study in mice suggests.
The finding may present a major barrier to using induced pluripotent stem
cells, or iPS cells, in treatments to repair
or replace damaged tissues.
The study introduces a needed note of
caution into what had become a headlong
race to rush reprogrammed cells into
clinical use, says Chad Tang, a stem
cell biologist at Stanford who was not
involved in the new work: “The iPS cell
phenomenon is so new and so hyped up
that it’s good we’re taking a step back to
ask what they can really do.”
Because reprogrammed cells are
derived from a patient’s own cells,
most researchers had assumed that the
immune system would not reject the cells
as it does those from another person.
Immune cells called T cells led the
attack on the reprogrammed stem cells,
which were derived from skin cells. The T
cells keyed in on certain proteins made in
some of the reprogrammed cells. Reprogrammed cells that didn’t produce those
proteins appeared to be safe from attack.
The researchers don’t yet know if stem
cells reprogrammed from other types of
tissues would prompt the same immune
onslaught as those created from skin
cells, says UC San Diego’s Yang Xu. If
rejection is limited only to certain types
of reprogrammed cells, then some others
might be used safely. But if the problem
is more widespread, researchers may
have to rethink the goal of transplanting the cells into patients. “It’s hard to
say how big the hurdle is,” Xu says, but
improving the reprogramming method
to make iPS cells more like embryonic
stem cells might solve the problem.
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