An international team of researchers has found that all-trans retinoid acid (ATRA), from vitamin A, may help keep the immune system under control for those with autoimmune disorders or who have received transplants, according to a new study published in the Journal of Leukocyte Biology. Scientists conducted a head-to-head comparison of the role of ATRA on two subpopulations of regulatory T cells, looking for chagnes. Results suggest that ATRA enhances one subpopulation of regulatory T cells, which are a component that suppresses the immune responses of other cells to prevent excessive reactions. "The great thing about this discovery is that we already have a strong foundation of clinical use for this form of vitamin A and know that it is well-tolerated by people," says E. John Wherry, Ph.D., deputy editor of the Journal of Leukocyte Biology. "It is a great example of the ability to exploit currently used drugs and our growign molecular and cellular understanding of the immune system."