Immune System Research: Vitamin A directs immune cells to intestines ♦ Role of microbiota in preventing allergies ♦ Scientists find molecular switch that creates long-term immunity

Organ transplant rejection may not be permanent Rejection of transplanted organs in hosts that were previously tolerant may not be permanent, report scientists. Using a mouse model of cardiac transplantation, they found that immune tolerance can spontaneously recover after an infection-triggered rejection event, and that hosts can accept subsequent transplants as soon as a week after. This process depends on regulatory T-cells, a component of the immune system that acts as a 'brake' for other immune cells.

Vitamin A directs immune cells to intestines A key set of immune cells that protect the body from infection would be lost without directions provided by vitamin A, according to a recent study. A team of researchers found retinoic acid is necessary for two of the three types of innate immune cells that reside in the intestine to find their proper place.

Role of microbiota in preventing allergies The microbiota is involved in many mechanisms, including digestion, vitamin synthesis and host defense. It is well established that a loss of bacterial symbionts promotes the development of allergies. Scientists have succeeded in explaining this phenomenon, and demonstrate how the microbiota acts on the balance of the immune system: the presence of microbes specifically blocks the immune cells responsible for triggering allergies.

Scientists find molecular switch that creates long-term immunity Researchers have identified a protein responsible for preserving the antibody-producing cells that lead to long-term immunity after infection or vaccination.