Organ transplant rejection in previously tolerant hosts does
not lead to permanent immune memory, mouse study shows
(July 8, 2015) Rejection
of transplanted organs in hosts that were previously tolerant may not be
permanent, report scientists from the University of Chicago. Using a mouse
model of cardiac transplantation, they found that immune tolerance can
spontaneously recover after an infection-triggered rejection event, and that
hosts can accept subsequent transplants as soon as a week after. This process
depends on regulatory T-cells, a component of the immune system that acts as a
"brake" for other immune cells. The findings, published online in
Nature Communications on July 7, support inducing immune tolerance as a viable
strategy to achieve life-long transplant survival.
"Transplantation tolerance appears to be a resilient
and persistent state, even though it can be transiently overcome," said
Anita Chong, PhD, professor of transplantation surgery at the University of
Chicago and co-senior author of the study. "Our results change the
paradigm that immune memory of a transplant rejection is invariably
permanent."
To prevent transplant rejection in patients with end-stage
organ failure, a lifelong regimen of immune-suppressing drugs is almost always
required. While difficult to achieve, immune tolerance -- in which a
transplanted organ is accepted without long-term immunosuppression -- can be
induced in some patients. However, rejection can still be triggered by events
such as bacterial infection, even after long periods of tolerance. It has been
assumed that the immune system remembers rejection and prevents future transplants
from being tolerated.