Carbohydrate moieties can induce mediator release: a detailed characterization of two major timothy grass pollen allergens.
Specific IgE binding to carbohydrate moieties of glycosylated allergens has been known for years, but the importance of these structures for the elicitation of allergic reactions is still a matter of debate. Because of their conserved carbohydrate structures, especially N-glycans have always been prime candidates for IgE cross-reactivity between allergens from unrelated species. The aim of our study was to determine whether carbohydrate structures on glycoproteins can by themselves elucidate allergic reactions. We characterized in detail the carbohydrate moieties of the major allergens Phl p 1 and Phl p 13 of timothy grass pollen (Phleum pratense L.) by performing tryptic digests followed by HPLC, N-terminal sequencing, sugar analysis, MALDI-TOF- and ESI-ICRFT-MS. Phl p 1 contains one N-glycan with one of the two glycoforms MMXF3 and M0XF3 and a single furanosidic arabinose, which is bound to a hydroxyproline residue in direct vicinity to the N-glycan. This O-glycosylation is probably due to an arabinosylation consensus sequence found in the N-terminal part of Phl p 1 and other group 1 allergens, but displayed no IgE-reactivity. Thus, Phl p 1 is monovalent with respect to its IgE-binding carbohydrate epitopes and showed no mediator release. In contrast, the carbohydrate moiety of Phl p 13, which carries four of the same N-glycans (like Phl p 1), can cross-link IgE-receptors via carbohydrate chains and elicits IL-4 release from basophils.
Wicklein
Daniel
D
Forschungszentrum Borstel, Parkallee 22, D-23845 Borstel, Germany. dwicklein@fz-borstel.de
Lindner
Buko
B
Moll
Hermann
H
Kolarich
Daniel
D
Altmann
Friedrich
F
Becker
Wolf-Meinhard
WM
Petersen
Arnd
A
D000485:Allergens / Q000737:chemistry* / Q000276:immunology; D000595:Amino Acid Sequence; D052179:Antigens, Plant; D001491:Basophils / Q000187:drug effects / Q000276:immunology; D001963:Bromelains / Q000494:pharmacology; D005643:Fucose / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology; D007073:Immunoglobulin E / Q000276:immunology*; D015847:Interleukin-4 / Q000378:metabolism; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry* / Q000276:immunology; D011134:Polysaccharides / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism
D000485:Allergens; D052179:Antigens, Plant; D010940:Plant Proteins; D011134:Polysaccharides; C485292:ph1p 1 allergen, timothy grass; C407403:phl p 13 protein, Phleum pratense; D015847:Interleukin-4; D005643:Fucose; D007073:Immunoglobulin E; D001963:Bromelains