Scientists at UC San Francisco are getting close to an answer. In a breakthrough that could transform how doctors treat conditions from eczema to allergies, they have discovered a feedback loop centered on a single immune protein called IL-31 that both causes the urge to itch and dials back nearby inflammation.
We tend to think that immune proteins like IL-31 help immune cells talk to one another, but here, when IL-31 talks to neurons, the neurons talk right back. It's the first time we've seen the nervous system directly tamp down an allergic response." The discovery could eventually change how asthma, Crohn's and other inflammatory diseases are treated, due to IL-31's presence throughout the body.
Related StoriesFirst, Fassett removed the IL-31 gene from mice and exposed them to the house dust mite, a common, itchy allergen. A balance of forces Ansel and Fassett then homed in on the nerve cells in the skin that received the IL-31 signal. They saw that the same nerve cells that spurred a scratch also dampened any subsequent immune response. These nerve cells were integral to keeping inflammation in check, but without IL-31, they let the immune system run wild.
Fassett and Ansel also found that these neurons released their own signal, called CGRP, in response to the itch signal, which could be responsible for dampening the immune response.