Alkaloids from the Korean mistletoe were reported to inhibit the growth of cultured leukemia L1210 and increased the life span of leukemic mice (leukemia P388 in BDF1 female mice) when applied intraperitoneally (Kwaja et al., 1980). Due to their extreme lability, the structures of these compounds have not been identified. Khwaja et al. (1986) hypothesised that the alkaloids may appear as labile glycoconjugates with Viscum album proteins and lectins. However, the presence of alkaloids within Viscum album is still controversial (see Pfüller, this book).
Actually, less is know about a cytotoxic 5 kDa peptide (NSC 635 089) extracted from a bacterially fermented VA-E by Kuttan and co-workers (1988, 1990, 1992a-c). The tumouricidal activity of this peptide is probably mediated by the induction of NK cells and macrophages (Kuttan and Kuttan 1992b, c, Kuttan, 1993a). Furthermore, the action of a rhamnogalacturonan extracted from VA-E is thought to be mediated by NK-cells and monocytes/macrophages (Hamprecht et al., 1987; Klett and Anderer, 1989; Müller and Anderer, 1990a-c; Zhu et al., 1994), and bridges CD56+ NK cells with tumour cells (Müller and Anderer, 1990b, c). Further, an oligosaccharide isolated from a VA-E induced interferon-y from CD4+ T cells and TNF-a from monocytes/ macrophages (Klett and Anderer, 1989; Müller and Anderer, 1990a).
In a fermented drug extract from mistletoe from pine trees, Stein and Berg (1994, 1996a, b, 1998a) detected an undefined antigen that elicited a strong stimulation of lymphocytes (CD4+ CD25+ T helper cells), monocytes (CD14+ CD80+) with cytokine production (IL-6, TNF-a, and variable Th1- and Th2-cytokine concentrations) in untreated healthy and allergic individuals.
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