The CD25 antibody recognizes the α chain of the IL2 receptor (IL2R). IL2Rα associates with the β chain (CD122) and the γ chain (CD132) to form the functional IL2R complex. IL2Rα is expressed on CD4+CD25+ regulatory T cells, activated T and B cells, and to a lesser extent on activated dendritic cells.
It is also transiently expressed during T and B cell development. Binding of the CD25 antibody does not impede the binding of IL2 to its receptor. In combination with CD4, CD25 antibody can be used to identify regulatory T cells (Tregs).