Vitamin D study sheds light on immune system effects -- ScienceDailyIn healthy people, T cells play a crucial role in helping to fight infections. In people with autoimmune diseases, however, they can start to attack the body's own tissues. By studying cells from mice and people, the researchers found vitamin D caused dendritic cells to produce more of a molecule called CD31 on their surface and that this hindered the activation of T cells. The team observed how CD31 prevented the two cell types from making a stable contact -- an essential part of the activation process -- and the resulting immune reaction was far reduced. Researchers say the findings shed light on how vitamin D deficiency may regulate the immune system and influence susceptibility to autoimmune diseases.