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PubMed1983

Mistletoe toxicity.

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Chemical and Drug Induced Liver Injury↗
PubMed1985

The in vitro activity of lectin I from mistletoe (ML I) and its isolated A and B chains on functions of macrophages and polymorphonuclear cells.

We investigated the effects of ML I and its isolated chains, A and B, in regard to selected functions of phagocytes (human granulocytes, paraffin-oil stimulated M phi from guinea pigs). On these cells, ML I has no cytotoxic effect between 10(-14) and 10(-8) (trypan blue exclusion and ethidium bromide exclusion). Over the same concentration range, ML I and B chain diminish the negative surface charge of M phi and agglutinate M phi at concentrations greater than or equal to 2 X 10(-8) M (ML I) and greater than or equal to 3 X 10(-7) M (B chain), respectively. The diminishing of the negative surface charge shows two peaks, indicating the existence of two types of receptors on the M phi surface with different affinities for sugar-binding sites. Moreover, the B chain shows a third peak at higher concentrations (3 X 10(-8) M) that could be inhibited by D-galactose (greater than or equal to 10(-4) M). In comparison, the A chain reduces the surface charge at concentrations over 3 X 10(-7) M, but D-galactose has no effect on this. By means of the agarose droplet test, the spontaneous migration of M phi is inhibited in the sequence ML I much greater than B chain greater than A chain. The phagocytic activity of human leukocytes tested with a radiometric phagocytosis technique reveals an increasing effect only for the B chain; ML I and the A chain have no effect. Perhaps the mechanism of the described activities of ML I and its B chain are comparable with the action of lymphokines activating M phi.

Animals↗
PubMed2005

Monomer/dimer equilibrium of the AB-type lectin from mistletoe enables combination of toxin/agglutinin activities in one protein: analysis of native and citraconylated proteins by ultracentrifugation/gel filtration and cell biological consequences of dimer destabilization.

The biological activity of a lectin is influenced by its quaternary structure. Viscumin is special among the family members of toxic AB-type plant lectins, because it triggers mitogenicity, toxicity, and agglutination. Its activity profile is dependent on the concentration, motivating a thorough inspection of the status of quaternary structure. Over a broad range of protein concentrations (0.01-25 mg/mL), viscumin occurs as a dimer. At high concentrations, the solutions exhibited nonideality, self-association, and polydispersity in sedimentation equilibrium and velocity experiments caused by irreversible aggregation. Calculation of viscumin's overall shape based on sedimentation velocity data resulted in an elongated dimer form resembling that of crystallized agglutinin. Appearance of monomers was restricted to concentrations in the submicrogram/mL level, as demonstrated by fast protein liquid chromatography gel-filtration analysis. To shift the equilibrium to the monomer for comparative cell biological assays, we performed chemical modification under conditions protecting the lectin activity. Citraconylation was effective to destabilize the dimer. Binding studies by fluorescence-activated cell scan analysis revealed a reduction in cell association upon modification and a tendency for increased sensitivity towards haptenic inhibitors at microg/mL concentrations. Nonetheless, growth inhibition continued to be potent for the ricin-like monomer despite reduced extent of binding. Occurrence of a concentration-dependent monomer/dimer equilibrium appears to achieve the same objectives as the development of two separate protein entities in Ricinus communis, an alternative strategy to emergence of a monomeric toxin, and cell cross-linking dimeric agglutinin.

Agglutinins↗
PubMed1999

Toxicity of a standardized mistletoe extract in immunocompromised and healthy individuals.

Iscador is being used by many patients as unconventional anticancer and immunomodulating therapy. To determine the toxicity profile and biochemical effects of Iscador Qu Spezial (Weleda AG Schwäbisch Gmünd, Germany) in human immunodeficiency virus (HIV)-positive patients and healthy controls, we performed a phase I/II study. Escalating doses of Iscador Qu Spezial, standardized for its lectin and viscotoxin content, were administered to 16 HIV-positive patients and 8 healthy subjects during a period of 6 to 8 months. Iscador Qu Spezial preparations were administered twice per week subcutaneously in increasing doses (ie, 0.01 mg, 0.1 mg, 1.0 mg, 2.0 mg, 5.0 mg, and 0.1 mg/kg for 2-6 weeks per dose). Drug-related adverse effects were flulike symptoms, gingivitis, fever, local erythema, and eosinophilia. These side effects were never severe. The incidence of systemic adverse events was highest in HIV-positive patients. Furthermore, increased urea levels and slightly decreased total protein caused by a minor decrease in albumin were observed. None of the HIV-positive patients progressed in disease stage. Iscador Qu Spezial can be administered safely to immunocompromised patients.

Adjuvants, Immunologic↗