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.