Biochemical properties of aeroallergens: contributory factors in allergic sensitization?

Abstract

Recent studies indicate that the majority of clinically important aeroallergens are biochemically active. A diverse range of properties have been demonstrated but most possess either enzymatic activity (principally hydrolytic), enzyme inhibitory activity, low molecular weight ligand transporting or regulatory properties. In addition, some allergens are glycosylated and/or are structurally similar to proteins which have evolved to function in the respiratory system per se. Little attention has been given to the possibility that the biochemical activity of an allergen or any post-translational modifications contribute to sensitization. In this review, mechanisms with the potential to influence immunogenicity are discussed including interaction with respiratory secretions, epithelial disruption, interactions with immunocompetent cells and receptor mediated endocytosis. Given that many aeroallergens are structurally and functionally similar to a variety of endogenous (e.g. lysosomal enzymes) and exogenous proteins (e.g. microbial enzymes and glycoproteins), particular attention has been directed to the latter. This process represents an important non-adaptive defence mechanism which has evolved to recognize and process such proteins and it is feasible that it plays a similar role in the processing of some allergens entering the respiratory system.

Enzymes as occupational and environmental respiratory sensitisers

“…There is evidence that at least proteases have, in addition to their allergenic potency, direct effects on epithelial integrity and permeability, mast cell degranulation, cytokine release from the respiratory epithelium and, further, exhibit interactions which may influence the pathogenesis of allergic and non-allergic airway disorders (Stewart et al 1993). Recent studies show that proteases can react with cell surface receptors (proteaseactivated receptors) in the airways.…”

Alkaline Serine Proteinase Is a Major Allergen of Aspergillus flavus, a Prevalent Airborne Aspergillus Species in the Taipei Area

“…However, progress made in allergen characterization has shown that the majority of clinically important allergens have biochemical functions. Most allergens are enzymes or regulatory proteins [28]. Serine proteinases such as trypsin and chymotrypsin have been identified as the group 3 and the group 6 major allergens of the house dust mite D. pteronyssinus [29, 30, 31].…”

Alveolar Macrophages Bind and Phagocytose Allergen- Containing Pollen Starch Granules Via C-Type Lectin and Integrin Receptors: Implications for Airway Inflammatory Disease

“…Of particular importance to this study are the carbohydrate-binding receptors such as the C-type lectins or the ␤-glucan receptor. These receptors have specificities for terminal sugar groups rarely found in mammalian systems but which are common constituents of pollen, bacteria, and fungi (22), suggesting the possibility that they play a role in innate recognition of AP such as PSG. The interaction of AP with receptors on AM has the potential to stimulate production of various mediators including NO.…”