Dimerization of the major birch pollen allergen Bet v 1 is important for its in vivo IgE-cross-linking potential in mice.
In type I allergy, the cross-linking of membrane IgE on B lymphocytes and of cytophilic IgE on effector cells by their respective allergens are key events. For cross-linking two IgE molecules, allergens need at least two epitopes. On large molecules, these could be different epitopes in a multivalent, or identical epitopes in a symmetrical, fashion. However, the availability of epitopes may be limited on small allergens such as Bet v 1, the major birch pollen allergen. The present work analyzes whether dimerization is required for the cross-linking capacity of this allergen. In immunoblots, murine monoclonal and polyclonal human Bet v 1-specific Abs detected, besides a Bet v 1 monomer of 17 kDa, a dimer of 34 kDa. In dynamic light scattering, Bet v 1 appeared as dimers and even multimers, but a single condition could be defined where it behaved exclusively monomerically. Small-angle x-ray scattering of the monomeric and dimeric samples resulted in diagrams agreeing with the calculated models. Circular dichroism measurements indicated that the structure of Bet v 1 was preserved under monomeric conditions. Skin tests in Bet v 1-allergic mice were positive with Bet v 1 dimer, but remained negative using the monomer. Furthermore, in contrast to dimeric Bet v 1, the monomer was less capable of activating murine memory B cells for IgE production in vivo. Our data indicate that the presentation of two identical epitopes by dimerized allergens is a precondition for cross-linking of IgE on mast cells and B lymphocytes.
Schöll
Isabella
I
Center of Physiology and Pathophysiology, University of Vienna, Austria.
Kalkura
Narayana
N
Shedziankova
Yuliya
Y
Bergmann
Alexander
A
Verdino
Petra
P
Knittelfelder
Regina
R
Kopp
Tamara
T
Hantusch
Brigitte
B
Betzel
Christian
C
Dierks
Karsten
K
Scheiner
Otto
O
Boltz-Nitulescu
George
G
Keller
Walter
W
Jensen-Jarolim
Erika
E
D000485:Allergens / Q000008:administration & dosage / Q000737:chemistry*; D000818:Animals; D017951:Antigen Presentation; D052179:Antigens, Plant; D029662:Betula / Q000276:immunology; D002942:Circular Dichroism; D003432:Cross-Linking Reagents; D019281:Dimerization; D005260:Female; D006969:Hypersensitivity, Immediate; D007114:Immunization; D007073:Immunoglobulin E / Q000737:chemistry* / Q000378:metabolism*; D066298:In Vitro Techniques; D008027:Light; D051379:Mice; D008807:Mice, Inbred BALB C; D008970:Molecular Weight; D010940:Plant Proteins / Q000008:administration & dosage / Q000737:chemistry*; D012542:Scattering, Radiation; D012882:Skin Tests
D000485:Allergens; D052179:Antigens, Plant; D003432:Cross-Linking Reagents; D010940:Plant Proteins; C061312:Bet v 1 allergen, Betula; D007073:Immunoglobulin E