0225 GMT November 14, 2019
A team of researchers from Purdue University found retinoic acid, a metabolite that comes from digested vitamin A, is necessary for two of the three types of innate immune cells that reside in the intestine to find their proper place, Science Daily said.
"It is known that vitamin A deficiencies lead to increased susceptibility to disease and low concentrations of immune cells in the mucosal barrier that lines the intestines," said Chang Kim, the professor and section head of microbiology and immunology. "We wanted to find the specific role the vitamin plays in the immune system and how it influences the cells and biological processes. The more we understand the details of how the immune system works, the better we will be able to design treatments for infection, and autoimmune and inflammatory diseases."
Within the immune system there are two categories of cells that work together to rid the body of infection: Innate immune cells, the innate lymphoid cells and leukocytes that are fast acting and immediately present to eliminate infection; and adaptive immune cells, the T-cells and B-cells that arrive later, but are specific to the pathogen and more effective at killing or neutralizing it.
All innate immune cells are produced in the bone marrow, but eventually populate other areas of the body. Innate lymphoid cells, which include the group studied by Kim, are present in barrier tissues. While it is known that innate lymphoid cells are concentrated in the intestines, it has been unknown how these cells find their way there, Kim said.
Innate lymphoid cells first gather in the lymph nodes before traveling to their final destination, and this is where retinoic acid acts upon two of the three subsets destined for the intestines. Kim and his team found that retinoic acid activates specific receptors in the cells that act as homing devices for the intestines. As the innate immune cells then travel through the circulatory system, the receptors grab onto and bind to molecules in the intestines and keep the cells in place, he said.