What is the role of the CD25 marker on T regulator cells?

The role of the CD25 marker on T regulatory cells is primarily to act as the interleukin 2 (IL-2) receptor. CD25 is the alpha chain of the IL-2 receptor, which is crucial for T cell function and regulation. T regulatory cells (Tregs) express high levels of CD25, allowing them to respond to IL-2 in a manner that promotes their survival, proliferation, and function. When IL-2 binds to CD25, it activates signaling pathways that are important for the maintenance and activity of Tregs, which in turn helps to suppress inappropriate immune responses and maintain self-tolerance. This is vital for preventing autoimmune reactions, ensuring that the immune system does not attack the body's own tissues. The presence of CD25 on Tregs is thus a key factor in their ability to maintain immune homeostasis.