Plasma soluble interleukin-2 receptor (sIL-2R) levels in patients with acute leukemia

The plasma soluble interleukin-2 receptor (sIL-2R) level was higher in 137 patients with acute leukemia (1,489 +/- 1,798 U/ml, including 98 cases of acute myeloid leukemia (AML), 1,063 +/- 1,414 U/ml, and 39 cases of acute lymphoblastic leukemia (ALL), 2,561 +/- 2,194 U/ml), compared to 49 normal control subjects, 421 +/- 151 U/ml). The ALL patients showed elevated plasma sIL-2R levels more frequently than the AML patients (92.3% vs 44.9%). No patient with either hypoplastic AML or AML with multilineage dysplasia and only 1 of 13 patients with acute promyelocytic leukemia (APL) had an elevated plasma sIL-2R level. All the My+ ALL patients (15 cases) showed elevated plasma sIL-2R levels. Plasma sIL-2R levels were significantly lower after chemotherapy in the ALL patients, but were not significantly lower in the AML patients. IL-2R was expressed on the leukemic cells in 36 (53.7%) of 67 AML and in 9 (21.4%) of 42 ALL cases. None of the AML M3, M4, M5, M6, or M7 subgroups showed IL-2R expression. The My+ ALL patients (42.9%, 6/14) showed IL-2R expression more frequently than the other ALL subgroups (10.7%, 3/28) (p = 0.025). The plasma sIL-2R level was correlated with the proportion of leukemic cells expressing IL-2R in acute leukemia. However, there were many cases, particularly ALL cases, who had elevated plasma sIL-2R levels without IL-2R expression on their leukemic cells. These results suggest that the plasma sIL-2R level is a valuable marker for monitoring ALL after chemotherapy, particularly in My+ ALL cases, and that the T cell immune reaction to leukemia appears to be much higher in ALL patients than in AML patients.