Versatile vitamin A plays multiple roles in the immune system

Mar 17, 2011

Although it has been known for some time that vitamin A deficiency is linked with an impaired ability to resist infections, exactly how vitamin A and its metabolites contribute to the immune response is not well understood. Somewhat paradoxically, research has indicated that vitamin A can also act as an immunosuppressive agent. Now, a study published by Cell Press in the March issue of the journal Immunity sheds light on how this critical vitamin integrates into both pro-inflammatory and anti-inflammatory immune responses in the gastrointestinal tract.

The metabolite retinoic acid (RA), along with one of its receptors RAR has been shown to have anti-inflammatory properties. Specifically, RA has been shown to induce production of regulatory T cells that help dampen the immune response to self and foreign antigen, including the bacteria that are normally present in the gastrointestinal tract. However, vitamin A insufficiency is associated with increased mortality to common gastrointestinal and lung infections and poor responses to vaccines, and there is evidence that in addition to its regulatory role, RA may help to stimulate the pro-inflammatory immune response to overcome infection. It is not clear how RA accomplishes these seemingly disparate roles.

"Gaining an understanding of the metabolites that control vitamin A dependent immunity and the relevant signaling pathways invoked is critical to resolving the paradox of why retinoids are immunosuppressive in some contexts, yet vital for host protective immunity," explains senior study author, Dr. Yasmine Belkaid from the National Institute of Allergy and . In their study, Dr Jason Hall, primary author of the study, and colleagues demonstrated that immune responses to infection and vaccination were compromised upon loss of vitamin A, and that RA served to activate the T cells driving these responses. Based on their findings, the researchers propose that RA influences the during the initial stages of activation and can amplify, in a context dependent manner, the capacity of the host t develop regulatory or inflammatory responses.

"The gastrointestinal tract must be able to tolerate constant exposure to food and the beneficial microbes that colonize this site, while maintaining the capacity to rapidly respond to encounters with pathogens," says Dr. Belkaid. "These conflicting pressures confront the immune system responsible for defending the with a unique challenge. In our study, we identified RA/RAR signaling pathway as a fitting system to accomplish these tasks, promoting generation of and likely tolerance during normal conditions and adaptive T cell responses when faced with pathogen." Taken together, these findings reveal a fundamental role for Vitamin A in the development of both regulatory and inflammatory arms of immune responses and establish nutritional status as a broad regulator of the immune system.

Explore further: US scientists make embryonic stem cells from adult skin

add to favorites email to friend print save as pdf

Related Stories

Vitamin D found to fight placental infection

Dec 01, 2008

In a paper available at the online site of the journal Biology of Reproduction, a team of UCLA researchers reports for the first time that vitamin D induces immune responses in placental tissues by stimulating production of the ...

Study: New way to control inflammation

Oct 03, 2006

U.S. researchers say they've discovered a new way to control or terminate potentially harmful immune responses that produce inflammation.

Recommended for you

Leeches help save woman's ear after pit bull mauling

Apr 18, 2014

(HealthDay)—A pit bull attack in July 2013 left a 19-year-old woman with her left ear ripped from her head, leaving an open wound. After preserving the ear, the surgical team started with a reconnection ...

New pain relief targets discovered

Apr 17, 2014

Scientists have identified new pain relief targets that could be used to provide relief from chemotherapy-induced pain. BBSRC-funded researchers at King's College London made the discovery when researching ...

User comments : 0

More news stories

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Study says we're over the hill at 24

(Medical Xpress)—It's a hard pill to swallow, but if you're over 24 years of age you've already reached your peak in terms of your cognitive motor performance, according to a new Simon Fraser University study.

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.