Recognition of different antigens of mistletoe extracts by anti-mistletoe lectin antibodies

Anti-mistletoe lectin-1 (ML-1) antibodies are produced during treatment of cancer patients with mistletoe extracts. However, little is known about the ir ability to recognise distinct epitopes present in mistletoe extracts. To estimate this, ML-1, ML-2 and ML-3 were analysed by Western blot analysis using high titred anti-ML antibody positive sera from cancer patients treat ed with different mistletoe extracts. In these experiments we could clearly demonstrate that anti-ML antibodies bind to ML-1 A- and B-chains and, in a ddition, that they recognised a spectrum of other antigens. This kind of im munological response varied from one individual to another and was not infl uenced by the different mistletoe extracts. Elution studies showed that ant i-ML-1 A-chain or B-chain specific antibodies cross-reacted with A- or B-ch ains of the other lectins indicating homologies between these molecules (pr obably in the glycosylated side chain). However, the unglycosylated ML-3 A- chain was only detectable by antibodies specific for the ML-3 A-chain. From our data it has to be concluded that different epitopes of the mistletoe e xtracts are involved in the induction of the humoral immune response during mistletoe therapy and also that cross-reactivity between the different ML exist. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.