Regulatory T cells prevent autoimmunity during infections

New research from the University of Chicago has shed light on how immune cells can prevent the body from attacking itself during infections. The study focuses on special immune cells known as regulatory T cells (Treg), which play a key role in distinguishing between harmful invaders and the body’s own cells. During an infection, the immune system must identify foreign substances, like bacteria and viruses, while avoiding attacks on its own cells. If this balance is not maintained, it can lead to autoimmune diseases, where the body mistakenly targets its own tissues. The recent findings emphasize the importance of Treg cells in managing this balance. The study, led by Pete Savage and David Klawon, highlights the interaction between Treg cells and another group of immune cells called helper T cells. Helper T cells are activated when they detect foreign substances, but they can also mistakenly attack the body's own cells. Treg cells help prevent this by intervening when they recognize self-antigens. Savage's research shows that Treg cells are trained to recognize specific self-peptides during their development. When these Treg cells are depleted in lab mice, the balance is disrupted. In healthy mice without infection, this does not cause immediate problems. However, when infected with a bacterium that expresses a self-peptide, the absence of Treg cells leads to an autoimmune response against the prostate, demonstrating how vital they are in preventing self-attack. Interestingly, this change did not hinder the helper T cells' ability to respond to foreign peptides. Savage explained that Treg cells act like peacekeepers. Even when a matching population of Treg cells is removed, helper T cells still manage to fight infections effectively. This study challenges the traditional view that the immune system prevents autoimmunity by eliminating self-reactive T cells. Instead, it suggests that having enough Treg cells is crucial for a healthy immune response. It flips the understanding on its head, emphasizing the need for targeted protection rather than just removal of potentially harmful cells.