April 06, 2007 Structural Biology Reveals How T Cells Recognize
Transplanted Tissue Before T cells are sent into battle, these
sentinels of the immune system must complete a rigorous
educational process. There are basically two things a T cell
must demonstrate before it makes the grade. It must recognize
specific molecules on the surface of foreign cells. And it must
refrain from attacking the body's own healthy cells. But
researchers who spy on T cells for a living know that there are
also gray areas where T cells can cause trouble. One such
example is transplanting healthy foreign tissue, such as a heart
or kidney. Researchers have long puzzled over how T cells can
recognize both self and foreign cells. This flexibility, they
say, may improve the immune system's chances of catching and
destroying a broad range of pathogens. But it also presents a
major clinical obstacle, leading to rejection of genetically
mismatched organ transplants. “We are not pathogens for each
other, so why when you get a liver transp