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 s yndromes (MDS) were investigated for soluble interleukin-2 receptor (s IL-2R) with a cell-free enzyme-linked immunosorbent assay (ELISA). The patients with MDS underwent treatment with IL-3: eigth patients at do se levels of 250 and 500 mu g/m(2) s.c. daily for 15 days, and seven p atients at the dose levels of 60 and 125 mu g/m(2) s.c. three times pe r week for 12 weeks. None of the patients had reported infectious epis odes or been under treatment with cytotoxic drugs and/or cytokines wit hin the preceding 2 months. sIL-2R levels were elevated in MDS patient s 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 ev ent due to involvement of lymphocytes in the malignant clone or due to a secondary alteration of the cytokine network caused by chronic neut ropenia. A down-regulation of the immune response caused by neutraliza tion of free IL-2 by sIL-2R during IL-3 therapy seems possible.