Detection of soluble IL-2 receptor in the serum of patients with myelodysplastic syndromes: induction under therapy with GM-CSF.

Sera of 15 healthy controls and 33 patients suffering from myelodysplastic syndromes (MDS) were investigated for soluble interleukin-2 receptor (sIL-2R) expression with a cell-free enzyme-linked immunosorbent assay (ELISA) system (T-Cell Sciences; Cambridge, U.S.A.). The upper limit of the assay is indicated with 477 U/ml. According to the FAB classification eight refractory anaemia (RA), 15 refractory anaemia with excess of blasts (RAEB), five refractory anaemia with excess blasts in transformation (RAEBt) and five chronic myelomonocytic leukaemia (CMML) were examined. None of the patients had reported infectious episodes or been under treatment with cytotoxic agents and/or cytokines within the previous 3 months. Significant differences in sIL-2R levels between RA (median 368 U/ml). RAEB (median 675 U/ml) and RAEBt (median 971 U/ml) and between RA and CMML (median 723 U/ml) were detected. Six patients, who had been under treatment with rhGM-CSF for at least 2 weeks, demonstrated a three- to sevenfold increase of sIL-2R expression compared to pretreatment levels. In kinetic evaluation of serum samples for 24 h, the increase of sIL-2R expression begins within 4 h after subcutaneous application of GM-CSF and reaches its maximum after 12 h. Our data cannot suggest whether increased sIL-2R expression is a primary event due to involvement of lymphocytes in the malignant clone or whether it results from secondary alteration of the cytokine network. Application of GM-CSF in MDS may result in improvement of altered lymphocyte function. As GM-CSF induces sIL-2R expression, a down regulation of the immune response caused by neutralization of free IL-2 cannot be excluded.