In atopic eczema both in local inflammatory reactions and in peripheral blood high interleukin (IL) 4: interferon-γ (IFN-γ) production ratios have been demonstrated, indicating predominance of TH2 cell subsets resulting in increased IL-4 production and high serum IgE. The in vitro immunomodulatory effects of recombinant human soluble IL-4 receptor (rsIL-4R) on IL-4-stimulated lymphocyte proliferation, IgE and IFN-γ production were studied in peripheral blood mononuclear cells from 10 patients with atopic eczema and seven healthy donors. In addition to control cultures (without any stimulus) and cultures with simultaneous application of rsIL-4R and IL-4, time-kinetic experiments were performed. We further investigated the influence of rsIL-4R on IL-4 production in staphylococcal enterotoxin B (SEB) stimulated peripheral blood mononuclear cells. Early addition of rsIL-4R to IL-4-stimulated peripheral blood mononuclear cells resulted in an increase in IFN-γ production and in suppression of IL-4 induced proliferation and IgE secretion. Unexpectedly, rsIL-4R in combination with SEB exhibited an IL-4 protective effect with a significant increase in detectable IL-4 in the culture supernatants. The present data support the assumption that rsIL-4R might be a promising new immunomodulatory substance in the treatment of atopic eczema.