In some people, the immune system has a disturbing tendency to revolt: For some reason, he violently attacks the body itself. For years, scientists have wondered what triggers this rebellion. Now a team of immunologists may have hit on an important piece of the puzzle: an aggressive T cell overproduction of a class that attack the body's tissues. This blow of T cells can be avoided, they found, by exposing mice to bacteria early in life
The immune system is like a mini-ecosystem -. If there is a shortage of one type of cell, another will multiply furiously to fill the niche. To study how this can contribute to disease, immunologists Nora Sarvetnick, Cecile King, and their colleagues at the Scripps Research Institute in La Jolla, California, studied mice predisposed to type 1 diabetes and other autoimmune diseases -immunes. A few weeks before falling ill, these animals had about half the normal number of so-called memory T cells. Cells recall encounters with intruders and defense against future ones.Not surprisingly, the team found that Sarvetnick other T cells have been filling the void memory cells left behind. What was particularly striking is that these replacements were supposedly CD4 + and CD8 +, the same ones that go haywire and destroy the pancreas, which triggers type 1 diabetes rapidly proliferating cells, they found, also sported a specific cell signaling molecule. Although this marker, called IL21 has not yet been associated with autoimmune diseases, the gene product is to the right in the known DNA segment to these mouse susceptible to diabetes, suggesting that IL21 could make a drug target, said Sarvetnick.Furthermore, giving the animal a shot dead bacteria - similar to an immunization in humans - when they were newborns, Sarvetnick and colleagues prevented CD4 glut + and CD8 +. And the animals are not sick, they report in the April issue of Cell 16. The approach gives credit to the so-called "hygiene hypothesis," which argues that exposure to toxins early in life - in the case of mice, inoculated bacteria - helps prevent allergies and autoimmune diseases.Use finding provides evidence for a link between a low number of T cells and autoimmune diseases, although still not clear that it exists, said Michael Bevan, an immunologist at the University of Washington, Seattle. Sarvetnick now hopes to collect samples of human patients to see if his theory holds there.
Related Sites
Background of autoimmunity of the National Institutes of Health
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