When the body makes immune T cells, it relies on a molecular
channel more commonly seen in nerves and heart muscles to ensure that the powerful T cells have the right mixture of aggressiveness and restraint, researchers at Washington University School of Medicine in St. Louis have discovered.
Scientists report online in Nature Immunology that fledgling T cells temporarily make a protein that creates an opening in their surfaces known as a voltage-gated sodium channel. The cells only make the protein at key points in a testing process that occurs in the thymus, an immune organ located near the heart. The channel allows the cells to “hear” the results of testing, which eliminates an estimated 95 percent of potential T cells.
“The thymus applies a kind of Goldilocks principle, seeking the cells that are just right, rather than those that are too hot or too cold,” says senior author Paul Allen, PhD, the Robert L. Kroc Professor of Pathology and Immunology. “The goal is not only to screen out the T cells that won’t react to invaders, but also to eliminate over-reactive T cells that could attack the body and cause autoimmune diseases. The voltage-gated sodium channel is the opening through which the T cell learns its fate.”
According to Allen, the finding is an important step forward in understanding how the immune system builds a repertoire of tens of millions of T cells, each primed to fight individual bacterial and viral invaders. Understanding this process will help scientists find better ways to control and enhance the immune system’s ability to fight diseases and cancer.