title: The major cow milk allergen Bos d 5 manipulates T-helper cells depending on its load with siderophore-bound iron.
abstract: The mechanisms of allergic sensitization to milk are still elusive. The major allergen Bos d 5 belongs to the lipocalin-family and thus is able to transport numerous ligands. In this study we investigated its ability to bind to iron-siderophore complexes and tested the immune-modulatory properties of Bos d 5 in either forms. Structural and in silico docking analysis of Bos d 5 revealed that Bos d 5 is able to bind to iron via catechol-based flavonoids (quercetin, myricetin, luteolin) that act as siderophores as confirmed by spectral-analysis and iron staining. Calculated dissociation constants of docking analyses were below 1 µM by virtual addition of iron. When incubated with human peripheral blood mononuclear cells (PBMCs), only the apo-form of Bos d 5 led to an increase of CD4+positive cells and significantly elevated IL13 and IFNγ-levels. In contrast, holo-Bos d 5 decreased numbers of CD4 expressing cells and induced apoptosis. Taken together, our data give evidence that Bos d 5 is capable of binding iron via siderophores. Moreover, our data support for the first time the notion that the form of application (apo- or holo-form) is decisive for the subsequent immune response. The apo-form promotes Th2 cells and inflammation, whereas the holo-form appears to be immunosuppressive.
authors.affiliation: Comparative Medicine, Messerli Research Institute of the University of Veterinary Medicine Vienna, Medical University Vienna and University Vienna, Vienna, Austria.
authors.forename: Franziska
authors.initials: F
authors.lastname: Roth-Walter
authors.affiliation: Biotechnology Department, Center for Plant Biotechnology and Genomics, Technical University of Madrid, Madrid, Spain.
authors.forename: Luis F
authors.initials: LF
authors.lastname: Pacios
authors.affiliation: Biotechnology Department, Center for Plant Biotechnology and Genomics, Technical University of Madrid, Madrid, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Gomez-Casado
authors.affiliation: Comparative Medicine, Messerli Research Institute of the University of Veterinary Medicine Vienna, Medical University Vienna and University Vienna, Vienna, Austria.
authors.forename: Gerlinde
authors.initials: G
authors.lastname: Hofstetter
authors.affiliation: Department of Anesthesiology, General Intensive Care and Pain Medicine, Medical University of Vienna, Austria.
authors.forename: Georg A
authors.initials: GA
authors.lastname: Roth
authors.affiliation: Comparative Immunology and Oncology, Department of Pathophysiology and Allergy Research, Center of Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria.
authors.forename: Josef
authors.initials: J
authors.lastname: Singer
authors.affiliation: Biotechnology Department, Center for Plant Biotechnology and Genomics, Technical University of Madrid, Madrid, Spain.
authors.forename: Araceli
authors.initials: A
authors.lastname: Diaz-Perales
authors.affiliation: Comparative Medicine, Messerli Research Institute of the University of Veterinary Medicine Vienna, Medical University Vienna and University Vienna, Vienna, Austria; Comparative Immunology and Oncology, Department of Pathophysiology and Allergy Research, Center of Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria.
authors.forename: Erika
authors.initials: E
authors.lastname: Jensen-Jarolim
mesh_terms: D000485:Allergens / Q000276:immunology* / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000276:immunology; D005419:Flavonoids / Q000378:metabolism; D006801:Humans; D007501:Iron / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000276:immunology; D054834:Lipocalins / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D008892:Milk / Q000276:immunology; D016269:Milk Hypersensitivity / Q000276:immunology*; D017262:Siderophores / Q000276:immunology / Q000378:metabolism*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
chemical_list: D000485:Allergens; C000604511:Bos d 5 allergen, Bos taurus; D005419:Flavonoids; D054834:Lipocalins; D017262:Siderophores; D007501:Iron