Immunomodulatory effects by mistletoe lectin

Journal/Book: in:" Lectins and glycoconjugates in Oncology", Gabius H.J., Nagel G.A.,(eds.),Springer Verlag, Berlin. 1988;

Abstract: Several studies have suggested that mistletoe lectins (ML) may beimportant in immunomodulation following tumor therapy with mistletoeextracts. Three types of ML are known: ML I, ML II, and ML III. The mostimportant, D-galactose-specific ML I (mol wt 115,000), consists of twoA-chains (mol wt 34,000) and two carbohydrate-binding B-chains (mol wt29,000). The present study investigated whether ML I and its subunitspurified from mistletoe extracts (Iscador) exhibit immunomodulatoryeffects. In vivo experiments were conducted using New Zealand male andfemale rabbits; immune parameters were measured for 3 days after asingle iv injection of ML I or its chains. Among the immunomodulatoryeffects observed after treatment with ML I or its B-chain were anincrease in large granular lymphocyte frequency in peripheral blood,increased cytotoxicity of natural killer (NK) cells (vs K562 cells),signs of an acute phase response, and an increase in interferon(IFN)-gamma level in serum. These results support the concept that ML Iand its chains exhibit immunomodulatory effects and may be important intumor therapy. It appears very probable that the B-chain is responsiblefor stimulating NK cells and triggering some nonspecific inflammatoryevents observed following ML I injection. ML I may modulate NK activitythrough the stimulation of IFN-gamma. However, a discrepancy between theoptimal doses of ML I for NK increase and for IFN-gamma inductionsuggests the involvement of other IFN-independent mechanisms in therecruitment and activation of NK cells. (17 Refs) ICDB.

Keyword(s): ADJUVANTS-IMMUNOLOGIC/

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