an antigenic determinant of the human interleukin 2 receptor that is identified by a murine monoclonal antibody, anti-Tac. Binding of this antigen with antibodies to TAC prevents the proliferation of T cells, which is normally stimulated by binding interleukin-2.
CD25A 55-kD monomeric glycoprotein low-affinity receptor for IL-2–IL-2R alpha. With p75 beta chain—CD122 antigen, IL-2Rbeta—CD25 forms a high affinity IL-2R complex.
CD25 is expressed on activated T and B cells in the germinal centre, mantle zone, on activated macrophages and thymic medulla cells; it is absent from thymocytes and resting T and B cells.
Hairy cell leukaemia and Hodgkin lymphoma, and may be expressed on T and B cell NHLs, and HTLV I/II-associated T cell leukaemias.