IL-2R alpha/CD25

CD25 is the alpha chain of the interleukin-2 receptor, a non-signaling subunit that binds IL-2 with low affinity alone but converts the beta-gamma receptor into the high-affinity form when co-expressed with CD122 and CD132. It is induced on antigen-stimulated T cells and constitutively displayed on regulatory T cells, which makes CD25 a defining Treg marker and a point of intervention for immunoregulation. Anti-CD25 antibodies such as basiliximab are approved to prevent kidney transplant rejection, and CD25 is further used to expand Treg products and to track T cell activation in immunomonitoring.