Induction of soluble IL-2 receptor in patients with myelodysplastic syndromes undergoing high-dose interleukin-3 treatment.

Sera of ten healthy controls and of 15 patients with myelodysplastic syndromes (MDS) were investigated for soluble interleukin-2 receptor (sIL-2R) with a cell-free enzyme-linked immunosorbent assay (ELISA). The patients with MDS underwent treatment with IL-3: eight patients at dose levels of 250 and 500 micrograms/m2 s.c. daily for 15 days, and seven patients at the dose levels of 60 and 125 micrograms/m2 s.c. three times per week for 12 weeks. None of the patients had reported infectious episodes or been under treatment with cytotoxic drugs and/or cytokines within the preceding 2 months. sIL-2R levels were elevated in MDS patients compared with healthy controls (p < 0.001). sIL-2R increased in the high-dose treatment group from 504 +/- 68 U/ml to 731 +/- 199 U/ml (p < 0.025). The increased sIL-2R expression in MDS could be a primary event due to involvement of lymphocytes in the malignant clone or due to a secondary alteration of the cytokine network caused by chronic neutropenia. A down-regulation of the immune response caused by neutralization of free IL-2 by sIL-2R during IL-3 therapy seems possible.