Tregs are involved in a wide range of diseases. In autoimmune diseases such as rheumatoid arthritis and multiple sclerosis, a deficiency or dysfunction of Tregs can lead to uncontrolled immune responses against self-tissues. Conversely, in cancer, Tregs can suppress anti-tumor immunity, allowing tumor cells to evade the immune system. Therefore, understanding and manipulating Treg function has significant therapeutic potential in both autoimmune diseases and cancer.