Serum Soluble Interleukin‐2 Receptor Levels in Patients with Adult T‐cell Leukemia and Human T‐cell Leukemia/Lymphoma Virus Type‐I Seropositive Healthy Carriers

Using an enzyme‐linked immunosorbent assay (ELISA) technique, we measured the soluble interleukin 2 receptor (s‐IL‐2R) levels in the sera of patients with adult T‐cell leukemia (ATL) in Japan. The s‐IL‐2R levels in the sera of the ATL patients were markedly higher (range 540‐310, 400 U/ml, mean ±SD=62,800 ±81,000 U/ml, n = 42) than those in normal individuals (range 42‐950 U/ml, mean ±SD=322 ±198 U/ml, n = 35, P<0.01). The patients with acute‐type or lymnhoma‐type ATL had high s‐IL‐2R levels (range 11,900‐310,400 U/ml, mean ±SD= 110,340 ± 370 U/ml, n = 15; range 26,400‐214,400 U/ml, mean ±SD=90,170 ±59,040 U/ml, n = 7, respectively). All of the patients with hypercalcemia (Ca>10 mg/dl) or elevated serum LDH levels (LDH > 500 IU/liter) also had s‐IL‐2R levels above 10,000 U/ml. The high s‐IL‐2R levels in the sera of ATL patients indicate abnormal IL‐2 receptor production and its release from the leukemic cells in vivo. Thus, the serum s‐IL‐2R level may be a sensitive and useful marker to monitor the total amount of tumor cells in ATL, especially in the lymphoma type. We next examined the serum s‐IL‐2R levels in human T‐cell leukemia/lymphoma virus type‐I (HTLV‐I) seropositive healthy carriers to investigate whether there might he abnormal IL‐2 receptor expression in such individuals. However, there was no statistically significant difference between the S‐IL‐2R level of 71 HTLV‐I seropositive healthy carriers (range 65‐880 U/ml, mean±SD =394±212 U/ml) and that of 71 age‐ and sex‐matched normal individuals (range 33‐950 U/ml, mean ±SD=357 ±224 U/ml) who lived in Okinawa Prefecture.