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 less than 0.01). The patients with acute-type or lymphoma-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 greater than 10 mg/dl) or elevated serum LDH levels (LDH greater than 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 be 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.