© NIAIDThe white blood cells called T-lymphocytes, such as this one shown by scanning electron microscopy, have receptors that bind to specific molecular targets. New work shows that the duration of this binding is what allows the cells to distinguish between the body's own proteins and those of invading pathogens.
To mount a successful defense against invading organisms, the immune system must quickly and accurately identify which cells belong in the body and which do not. That might seem straightforward enough, but it's not such an easy feat to achieve. The responsibility falls largely on the shoulders of T-cells, white blood cells with specialized receptors embedded in their surface that allow them to bind uniquely to diverse peptide fragments. Once bound, the T-cells can then initiate a focused attack against the target.
"It's an amazing needle in a haystack that they're trying to identify," said Orion Weiner, a biochemist at the University of California, San Francisco. "Being able to find that incredibly rare [foreign] peptide in a sea of quite similar self-peptides is an amazing challenge. It requires a degree of both specificity and sensitivity that's really at the limits of what's physically possible."
Comment: See also: Cat cognition: Cats rival dogs on many tests of social smarts. But is anyone brave enough to study them