Bet v 1, the major birch pollen allergen, and Mal d 1, the major apple allergen, cross-react at the level of allergen-specific T helper cells.
BACKGROUND
Food allergy to apple is frequent in individuals allergic to tree pollen. The major allergens of birch, Bet v 1, and apple, Mal d 1, have been cloned and sequenced and display a high degree of sequence identity, leading to IgE cross-reactivity.


OBJECTIVE
We sought to investigate cross-reactivity between Bet v 1 and Mal d 1 at the level of allergen-specific T lymphocytes.


METHODS
PBMCs of 13 patients allergic to birch pollen with oral allergy syndrome to apple were stimulated with rBet v 1 and rMal d 1, respectively, thereby establishing allergen-specific T-cell lines and T-cell clones. rMal d 1-specific T-cell cultures were tested for reactivity with rBet v 1, and rBet v 1-specific T cells were analyzed for reactivity with apple allergen. Cytokine production patterns in response to specific stimulation were evaluated. A selection of cross-reacting T-cell clones was mapped for epitope specificity by the use of overlapping Bet v 1- derived peptides.


RESULTS
Nineteen Mal d 1-specific T-cell clones were produced, 79% of which cross-reacted with Bet v 1. Eight of 18 Bet v 1-specific T-cell clones cross-reacted with Mal d 1. Six peptides representing cross-reactive T-cell epitopes could be identified. The respective fragments from birch and apple displayed approximately 50% amino acid identity. Seventy percent of the cross-reactive T-cell clones revealed a T(H2)-like cytokine production pattern.


CONCLUSIONS
The results indicate that cross-reactivity between apple and birch pollen leading to the clinical oral allergy syndrome occurs not only at the serologic, but also at the cellular level.
Fritsch
R
R
Institute of General and Experimental Pathology, Department of Immunopathology, University of Vienna, Austria.
Bohle
B
B
Vollmann
U
U
Wiedermann
U
U
Jahn-Schmid
B
B
Krebitz
M
M
Breiteneder
H
H
Kraft
D
D
Ebner
C
C
D000328:Adult; D000485:Allergens / Q000276:immunology*; D000595:Amino Acid Sequence; D052179:Antigens, Plant; D003429:Cross Reactions; D016207:Cytokines / Q000096:biosynthesis; D018604:Epitope Mapping; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D005260:Female; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000276:immunology*; D019685:Rosales; D012882:Skin Tests; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*; D014197:Trees
D000485:Allergens; D052179:Antigens, Plant; D016207:Cytokines; D018984:Epitopes, T-Lymphocyte; C095551:MALD1 protein, Malus domestica; D010940:Plant Proteins; C061312:Bet v 1 allergen, Betula