Adaptive immunity relies on the capacity of immune cells to distinguish between the body's own cells and foreign invaders. T-cells are the foot soldiers of the immune system, and they carry receptors that undergo an extensive "education" process for recognizing specific proteins from these invaders. Mature T-cells also show the ability to recognize proteins for which they have not been exposed to. How the T-cell receptors (TCRs) achieve this ability is poorly understood. It is this same immune response which causes T-cell mediated rejection in organ transplant patients, and solving this problem could lead to new ways of combating tissue rejection.

Now, researchers are one step closer to understanding how T-cell receptors recognize foreign proteins. Using SSRL Beamline 11-1, a team from the Stanford University Medical School has determined the structure of a TCR bound to a "foreign" protein complex, and has compared this to the previously solved structure of the same TCR bound to a "self" protein complex. Unlike earlier speculation attributing the mechanism to "molecular mimicry," the current study shows that the TCR binds to foreign proteins in a completely different way than it does self proteins, despite an 80% structural similarity between the two.

The work appeared in the April 6 edition of the journal Cell.

To learn more about this research see the full scientific highlight at:
http://www-ssrl.slac.stanford.edu/research/highlights_archive/Tcr.html

Colf, L.A., Bankovich, A.J., Hanick, N.A., Bowerman, N.A., Jones, L.L., Kranz, D.M., and Garcia, K.C. (2007). How a single T cell receptor recognizes both self and foreign MHC. Cell 129, 135-146.