Abstract

Activation of T cells is associated with a dramatic increase in expression of the interleukin-2 receptor. In addition to the intact receptor found at the cell surface, activated T cells produce a truncated form of the receptor (sIL-2R) that is secreted as a soluble molecule. Patients with neoplastic disease or diseases involving immune activation exhibit markedly elevated serum levels of sIL-2R. Although the functional significance of sIL-2R is unknown, the ability to measure this parameter rapidly and accurately in serum samples makes it a potentially useful index for monitoring disease activity. Recent studies indicate that a rise in serum levels of sIL-2R in apparently healthy individuals could be an important early signal of neoplastic, autoimmune, or inflammatory disease. Moreover, subsequent to diagnosis, serum levels of sIL-2R appear to be a reliable indicator of tumor burden and therapeutic response for many patients with leukemia and lymphoma, an indicator of metastasis for patients with solid tumors, and an indicator of exacerbation and clinical response in patients with diseases associated with immune activation.