Scientists at UT Southwestern Medical Center have identified a mechanism by which gut bacteria assist in regulating the immune system by directing the flow of vitamin A to specific immune cells. The findings, published in the journal Cell Host & Microbe, describe a previously unknown cellular network that links microbial activity to immune development.
The research indicates that gut bacteria trigger a stepwise transfer of vitamin A between cells. This process starts in the intestinal lining, where microbes stimulate the production of a protein called serum amyloid A. This protein binds to vitamin A and delivers it to immune cells within the intestine.
These immune cells then transport the vitamin A to nearby lymph nodes, where they pass vitamin A-derived signals to developing T cells.
T cells are a class of immune cells responsible for protecting the body from infection. The study notes that the immune system relies on signals derived from vitamin A to guide the development of these cells.
While the importance of both gut microbes and vitamin A for a healthy immune system has been recognized for years, the specific connection between them was not understood until now.
When researchers removed gut bacteria from mice in the study, the vitamin A delivery system was largely shut down. As a result, developing T cells were unable to mature properly or migrate to the intestine.
The researchers stated that because these steps are essential for building a functional immune defense, disruptions in this pathway could impair the body's ability to respond to infections or maintain normal immune balance.
