Scientists believe they have discovered why vitamin A is key to the proper functioning of the immune system.

Dendritic cells throughout the body, which alert the immune system to infection, send both ‘alarm’ as well as ‘calm down’ messages, the latter using vitamin A as enabler.

“The immune system has to provide a defense against infection, while avoiding the destruction of too much of the body along the way,” says Dr. Bali Pulendran, professor of pathology and laboratory medicine at the Emory Vaccine Center and Yerkes National Primate Research Center.

When there is an insufficient level of vitamin A, the immune system goes into “overdrive,” resulting in an autoimmune disease such as rheumatoid arthritis, lupus and type I diabetes where the body attacks its own tissue.

In the course of their study, the Emory researchers treated a cell culture with a compound called zymosan and found that it turned on genes involved in converting vitamin A to its active form, retinoic acid.

They now believe they may be able to use the discovery to design ways to stop the body in which the ‘attack’ response is dominant from destroying its own cells.

Vitamin A can be found in a variety of foods, including carrots, leafy vegetables, sweet potatoes, mango, eggs and others, or taken in the form of nutritional supplements.