IL-2R (T-cell growth factor receptor) consists of a chain of 55 kDa (also known as Tac antigen or p55 or alpha chain) and a p75 or beta chain. IL-2RA is over-expressed on the surface of activated Tcells, HTLV-1 or -2 positive T-cell lines, and moderately expressed on activated B-cells, NK-cells, and macrophages. CD25 Molecule alone appears to function as a low affinity receptor and associates wtih CD122 (IL-2R beta chain, p75) and CD132 (common gamma chain) to form the high affinity IL-2 receptor complex.Synonyms: IL-2 receptor alpha subunit, IL-2-RA, IL2-RA, Interleukin-2 receptor alpha chain, TAC antigen, p55