Th9-derived IL-9 in autoimmune diseases: An update

Autoimmune diseases (AIDs), such as rheumatoid arthritis, multiple sclerosis, and systemic lupus erythematosus, are caused by abnormal immune response that targets the body's own tissues. T-helper cell 9 (Th9) is a recently discovered subpopulation of T cells that primarily participates in inflammatory responses and immune regulation by secreting interleukin-9 (IL-9). IL-9 is a multifunctional cytokine that regulates the function of T and B cells, and also affects the activation and response of mast cells, macrophages, and other cells. Studies have shown that Th9 cells significantly affect the development of autoimmune diseases and are closely related to disease activity and pathological processes. Exploring drugs targeting Th9 cells or IL-9 and elucidating the regulatory mechanisms of Th9 and IL-9 in various AIDs will provide important insights for the development of novel therapeutic strategies.