Emory Report homepage  

March 23, 2009
Vitamin A signals offer clues to treating autoimmunity

By Quinn Eastman

Researchers have discovered that dendritic cells, the microbe-sensing alarms of the immune system, can respond to a single compound by sending out both stimulatory and calming messages at once.

The results were published in the March issue of Nature Medicine.

This “gas and brake together” feature can be viewed as the result of an evolutionary struggle between microbes and the regulatory controls embedded in the immune system, says immunologist Bali Pulendran.
The compound Pulendran and colleagues examined for its ability to act through two different receptors is zymosan, a component of yeast cell walls. However, the finding could guide scientists in designing vaccines against many infectious agents since dendritic cells are known to respond to bacteria and viruses as well as yeast through the same receptors. In addition, silencing the messages from the calming receptor might boost the immune system’s ability to fight a chronic infection.

The calming receptor, known as TLR2 (Toll-like receptor 2), uses vitamin A to transmit its signals. This provides an explanation for the connection between vitamin A deficiency and autoimmune diseases, where the body’s own tissues are attacked indiscriminately. Vitamin A deficiency has been linked to diseases such as rheumatoid arthritis, lupus and type I diabetes.

The effects of zymosan and TLR2 can deter white blood cells from attacking nerve tissue in a mouse model of multiple sclerosis, the researchers found.