Esther Landhuis in Scientific American:
For a long time researchers figured the body had a tidy way of dealing with immune cells that might trigger diabetes, lupus or other autoimmune diseases—it must kill off these rogue cells early in life, before the immune system matures. New research published on May 19 in Immunity challenges this age-old thinking. Instead, the body seems to keep these so-called self-reactive T cells in benign form to fight potential invaders later. That conclusion comes from a comprehensive set of immune analyses in mice and people, in which a team at Stanford University has found surprisingly large numbers of self-reactive T cells lurking in the bloodstream through adulthood. The cells are not easily activated, though, suggesting the presence of “a built-in brake,” says immunologist Mark Davis, the paper’s senior author. The findings renew debate about how the immune system manages to marshal its forces against myriad foreign invaders all the while leaving our own tissues alone.
The controversy emerged decades ago when researchers learned the secret to the immune system’s incredible versatility. They discovered that a special gene-shuffling process makes millions of antibodies and receptors. Their sheer number and variety allow our immune cells to recognize any conceivable pathogen, in principle. But the explanation also posed a puzzle: Those random gene rearrangements also produce T cells that could attack the body’s own tissues. As a solution, some scientists proposed that the body wipes out those self-reactive cells while the immune system is developing. Subsequent experiments by several labs supported this proposal.
More here.
