Mistletoe treatment induces GM-CSF- and IL-5 production by PBMC and increases blood granulocyte- and eosinophil counts: a placebo controlled randomized study in healthy subjects.

OBJECTIVE Various immunological effects have been reported during application of mistletoe preparations. Because these data are heterogeneous, we performed a placebo controlled study to investigate (1) effects on peripheral granulocyte and eosinophil counts, (2) related cytokine levels and (3) whether effects are related to mistletoe lectin (ML). METHODS 43 volunteers were randomized to receive the mistletoe plant extract Iscador Quercus spezial (IQ), purified ML, IQ which was depleted from ML, or placebo subcutaneously twice per week for 8 weeks. Weekly, differential blood count and every four weeks spontaneous and IQ- and ML-induced cytokine production by peripheral blood mononuclear cells (PBMC) were analyzed. RESULTS Leukocyte-, granulocyte-, and eosinophil counts were significantly higher during treatment in the IQ- and ML-groups than in the placebo group. Furthermore, a significant increase of antigen-induced production of GM-CSF, IL-5 and IFNgamma by PBMC was observed in the IQ- and ML-group but not in the groups receiving ML-depleted IQ or placebo. Severe side effects did not occur in any of the subjects. CONCLUSIONS Treatment with IQ or ML stimulates the production of GM-CSF, IL-5 and IFNgamma by PBMC, and this is accompanied by an increase of eosinophil- and granulocyte-counts. These observations may, therefore, open rational therapeutic indications for mistletoe extracts.