Modulatory potency of the B-galactoside specific lectin from mistletoe extract (Iscador) on the host defense system in vivo in rabbits and patients

Journal/Book: Cancer Research 49, 4803-4808. 1989;

Abstract: Proprietary extract of mistletoe (Iscador) that has federal approval forclinical application can exhibit immunomodulatory capacity. However, thenature of this responsible substance has still remained elusive. Tovalidate the hypothesis that specific lectin-carbohydrate interactionsat least participate in eliciting immunomodulation, the modulatoryefficiency of the major beta-galactoside-specific mistletoe lectin (MLI) from the clinically applied extract on selected immunologicalparameters was monitored "in vivo" in rabbits. Injections of nontoxicdoses of the purified lectin or even only of its carbohydrate-bindingsubunit (0.25-1.0 ng/kg) into rabbits yielded significant increases innatural killer cytotoxicity, frequency of large granular lymphocytes,and phagocytic activity of granulocytes. In the clinically relevantsituation, changes in these parameters were also determined in cancerpatients after extract (Iscador) injection s.c. as well as i.v.,emphasizing the potential relevance of the lectin. Comparative analysesof the changes in the selected parameters following injection of extractwith normal lectin content as well as of extract, selectively depletedof lectin, into healthy volunteers corroborated this inference. Lectindepletion by affinity chromatography was highly specific and did notaffect any other substance in the extract. Remarkably, contamination byendotoxin has been rigorously excluded in each applied specimen. Theseresults encourage detailed elucidation of lectin action on various partsof the tumor defense system "in vitro" with the long range goal ofachieving progress in the treatment of cancer through immunologicalstrategies, exploring selective mediatory lectin-carbohydrateinteractions. Author.

Keyword(s): ADJUVANTS-IMMUNOLOGIC/

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