The Interleukin 2 Receptor alpha and beta chains, together with the common gamma chain, constitute the high affinity IL2 receptor present on activated T and B cells, thymocyte subset, pre B cells and T regulatory cells. Homodimeric alpha chains result in low affinity receptor, while homodimeric beta chains produce a medium affinity receptor. Normally an integral membrane protein, soluble IL2 Receptor alpha has been isolated and determined to result from extracellular proteolysis. Alternately spliced IL2 Receptor alpha mRNAs have been isolated, but the significance of each is presently unknown.