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. Author manuscript; available in PMC: 2019 Aug 1.
Published in final edited form as: Mol Immunol. 2018 Apr 4;100:3–13. doi: 10.1016/j.molimm.2018.03.003

Table 1.

Possible origins of isoallergens, variants and other types of allergen heterogeneity.

Type of heterogeneity Origin Characteristics Known examples in
the Allergen
Nomenclature
database
Dispersed amino acid sequence variability. Named as isoallergens or variants, depending on level of sequence divergence. Allelic One isoallergen/variant per haplotype.a Der f 2; Bet v 1 variants are in part allelic
Differential IgE antibody recognition of isoallergens may occur but is less likely for variants.
Multigene family Multiple isoallergens/variants, encoded by different genes per haplotype, may be present per organism.a Bet v 1
Differential IgE antibody recognition of isoallergens may occur but is less likely for variants. Ara h 2
Size and/or charge distribution Posttranslational modifications such as addition of carbohydrate, phosphate groups, hydroxy-proline, C-terminal proteolytic cleavage or other moietiesb Each individual proteins may contain multiple postranslationally modified allergen forms. No examples
Differential IgE antibody recognition of glycoforms may occur.
Chemical composition Chemical modification of the allergenb Modification of the allergen during airborne transport (for aeroallergens), storage and processing (for food allergens), or preparation of extracts, e.g. oxidization, reactions with polyphenols, Maillard reaction during roasting of foods. No examples
Block differences: amino acid sequence differences in segment/s of the protein. Different protein cleavage Each individual contains multiple differentially cleaved forms. Hev b 6.02 and Hev b 6.03
IgE antibody recognition may be affected depending on epitope distribution.
Alternative mRNA splicing None yet identified for allergens. No examples
Modular differences: Different subunit (entire gene product) composition. Alternative subunit composition Each individual contains multiple allergen forms, depending on subunit combinations. Gly m 5, Gly m 6
IgE antibody recognition may be affected depending on epitope distribution.
a

Polyploidy (more than two haplotypes) will further increase the number of genes (each of which can harbor different allelic isoallergens/variants).

b

This kind of modification does not lead to different isoallergens or variants.