Measurement of Soluble Interleukin 2 Receptor in Sera of Adult Patients with Hematological or Solid Malignancies

Interleukin 2 (IL-2) exerts its biological activity through a specific membrane receptor. Using specific monoclonal antibodies directed against the IL-2 receptor, a soluble form of this receptor can be detected in the serum. This soluble part of the human IL-2 receptor (sIL-2R) is released by T and B lymphocytes and plays a role in lymphoid cell growth regulation. We have measured the sIL-2R by ELISA in the serum of patients with solid tumors and with hematological malignancies (44 chronic lymphocytic leukemias (CLL), 5 hairy cell leukemias (HCL), 14 Hodgkin's diseases (HKD), 34 non-Hodgkin's lymphomas (NHL) and 19 acute lymphoblastic leukemias (ALL). The mean sIL-2R level in 40 normal subjects was 173 + 168 U/ml (mean {pminus} SD). It was considerably increased in HCL: 17938 {pminus} 23748 (P < 0.0003). In CLL, a significant increase was found which was particularly pronounced at clinical stage III and IV with a mean level of 1299 {pminus} 1127 U/ml. In HKD, sIL-2R was slightly but significantly increased 519 + 524 U/ml (P < 0.0004). In NHL, the sIL-2R level was 1015 {pminus} 1022 U/ml, but this increase did not correlate with the clinical stage or the histological grade of the disease. In ALL, sIL-2R levels were also significantly increased 1633 + 1046 U/ml (P < 0.00001). In 69 patients with solid tumors (including lung carcinomas, gynecological and digestive malignancies), 39% of the patients tested had slightly increased sIL-2R levels. However, this increase, when present, could not be related to the tumor histology. These results suggest that sIL-2R measurement is a poor diagnostic marker for solid tumors and some lymphoproliferative disorders. However, in patients with hematological malignancies, it could be a useful tool to monitor lymphoid neoplasias.