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DOI: 10.1055/s-0030-1264812
Localization of arabinogalactan-proteins (AGP) in aerial parts of Echinacea purpurea and of AGP binding sites in rabbit Peyer's patches by immunofluorescence
Echinacea purpurea preparations are used as unspecific immunostimulants. Besides alkamides [1], high molecular weight arabinogalactan-proteins (AGPs) are supposed to belong to the immunomodulatory active compounds of E. purpurea. In plants these AGPs are thought to influence plant growth, development and programmed cell death [2]. The localization of AGPs in plant tissues of E. purpurea helps to understand the physiological role of AGPs and optimize the production of pharmaceutical preparations. For immunolocalization of AGPs, the β-glucose-Yariv-reagent (βGlcY), binding selectively to AGPs, was used to label AGPs in sections of stem and leaf stalks from E. purpurea. Comparable to roots of E. purpurea [3], AGPs are mainly located in cell walls of xylem tracheary elements, especially in pit channels. In contrast to roots, the aerial parts of the plant show additionally very strong immunolabeling of sclerenchyma cells and of companion cells of the phloem. The pharmacological effects of AGPs after oral application of E. purpurea preparations are thought to be mediated by Peyer's patches of the ileum [4]. Cryo sections of rabbit Peyer's patch tissue were incubated with AGPs from Echinacea and AGP binding sites were detected using immunohistochemistry and confocal microscopy. AGPs from the aerial parts of E. purpurea strongly bind to intraepithelial lymphocytes in pockets of membranous (M) cells. As these sites are believed to be critically involved in the initiation of specific immune responses as well as the generation of immune tolerance [5], AGPs from E. purpurea might directly influence the immune protection of the human organism.
Acknowledgements: We thank Rottapharm/Madaus GmbH, Köln, for financial support of this work.
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