Non-lectin component in a fermented extract from Viscum album L. grown on pines induces proliferation of lymphocytes from healthy and allergic individuals in vitro.

Mistletoe preparations have been shown to express immunomodulatory properties. In order to evaluate the stimulatory potency of different mistletoe extracts, peripheral blood mononuclear cells (PBMC) from healthy and allergic/atopic individuals were exposed to aqueous or fermented extracts derived from Viscum album L. grown on apple trees (Mali-extracts) or on pines (Pini-extracts). None of them had received any mistletoe treatment. Iscador Pini was the only extract which strongly induced proliferation of PBMC in contrast to the other five preparations. On testing these extracts by Western blotting with anti-mistletoe lectin-1 (ML-1) antibody positive sera from mistletoe-treated patients, it became evident that Iscador Pini was almost devoid of lectins. The stimulatory potency of Iscador Pini for PBMC from three different groups was examined: PBMC from 35 normal controls (Group I), 23 patients with drug-induced adverse effects (Group II) and 16 individuals with allergic manifestations (Group III). Cells were exposed in 7-day cultures to the extract at concentrations between 1 and 10,000 micrograms/ml. PBMC from 63% of Group III individuals showed strong stimulation (SI varying from 6 to 97) in contrast to only 9% from Group I and 22% from Group II individuals. Anti-ML-1 antibodies were detected in 5% and anti-IP antibodies in 11% of subjects in the three groups. They were either of the IgA or IgM type but not of the IgG type. Our findings strongly imply that a non-lectin associated antigen from Iscador Pini is able to activate PBMC from healthy and allergic/atopic individuals, thereby demonstrating sensitization to probably highly conserved plant antigens.