快猫短视频

A LITTLE re-education could work wonders for the cells that provoke the
immune attack on a transplanted organ. They could be taught to tell the immune
system to ignore the organ instead.

Activating either one of two genes in these cells does the trick, Nicole
Suciu-Foca Columbia University in New York and her colleagues have discovered.
The finding may also help explain why the immune system sometimes attacks its
owner鈥檚 body, and how certain viruses and bacteria evade it. 鈥淭he implications
are potentially enormous,鈥� says Suciu-Foca.

Immune cells recognise other body cells as 鈥渟elf鈥� because they all have the
same MHC proteins on their surface. If foreign cells invade, antigen-presenting
cells (APCs) take bits of the foreign proteins and display them on their
surface, together with the body鈥檚 own MHCs. When T helper cells see this
combination, they tell other immune cells to hunt down and destroy any cells
displaying the foreign proteins.

But in transplant patients, things can go horribly wrong because the APCs in
the donor organ carry their original owner鈥檚 MHC proteins. The host immune
system interprets this as a signal to launch an attack on all cells bearing
these MHCs, triggering rejection of the donor organ.

But Suciu-Foca has found that another kind of cell, called a T suppressor
cell, can also come into play. When the right suppressor cells are present, APCs
persuade T helpers to ignore cells sporting foreign proteins instead of sounding
the battle cry. Suciu-Foca found they do this by getting the APCs to switch on
two genes: immunoglobulin-like transcript 3 and 4 (
ILT-3 and ILT-4).

She thinks that it might be possible to prevent transplants being rejected if
some way could be found to switch on the ILT-3 and ILT-4 in
the APCs in donor organs before transplantation, or to generate a population of
the right T suppressor cells. This would avoid the need to give transplant
patients immunosuppressive drugs, which leaves them vulnerable to
infections.

The big question is how to do this. But the team did find that this process
might already happen naturally in some transplant patients. They compared 10
heart transplant recipients who had experienced rejection episodes within eight
months with five who had not. Only in these five were they able to find T
suppressor cells capable of switching on ILT-3 and 4 in APCs
from the donor.

鈥淚t鈥檚 a very important insight for basic immunology,鈥� says Guido Silvestri at
Emory University in Atlanta, Georgia. But he warns that the picture is clouded
by the fact that all 15 patients were taking immunosuppressive drugs. To prove
that having the right T suppressor cells really does make a difference,
Suciu-Foca is planning a clinical trial to find out if they allow patients to
get by with lower doses of immunosuppressive drugs.