Cross-reactivity of pollen allergens: impact on allergen immunotherapy

Objective: To provide guidelines for the rational formulation of allergen immunotherapy extracts based on knowledge of pollen allergen and epitope cross-reactivity. Data Sources: A PubMed search was performed for articles published from 1966 to 2007 using the keywords pollen, allergen, and cross-reactivity. Older literature was found through cross-referencing of older articles and older reviews on pollen cross-reactivity. Study Selection: Articles that dealt with crude pollen extracts and characterized allergens that addressed cross-reactivity were selected for inclusion in this review. Results: In addition to unique allergens, several families of botanic proteins have similarities that allow them to act as pan-allergens. Although frequently these are minor allergens, in some circumstances they may also be major allergens. Recent studies have investigated nonspecific lipid transfer proteins, calcium-binding proteins, pathogenesis-related protein families, and profilins. Calcium-binding proteins and nonspecific lipid transfer proteins are responsible for pollen-fruit interactions and pollen cross-reactivity. Clarification of pollen allergen enzymatic activity helps explain the ubiquitous nature of these proteins. Conclusion: Characterization of specific pollen allergens and their protein families has provided insight into cross-reactivity. Clarification of these relationships allows for consolidation or substitution in formulation of inhalant extracts.