Allergens: the relationship between biological function and allergenicity

Abstract

Allergens can be found from many diverse sources but they have the particular quality of being able to induce immunoglobulin E (IgE) production and to provoke allergy. A common biological molecular characteristic which can explain their allergenic capacity is not known amongst the allergens. In the last few years allergens' different biological functions have been demonstrated or inferred, generating a new hypothesis about the role of the said functions in allergenic activity. To identify which biological functions have been demonstrated or inferred in the allergens and to analyse their possible influence on allergenic role, approximately two hundred allergens were revised using those already classified by the WHO's Allergen Nomenclature committee as the basis for characterisation, as were others less characterised, but having some known physicochemical properties. The allergens were grouped according to biological activity and were tabulated with their source of origin, molecular weight (MW), isoelectric point (Ip), reactivity frequency in the allergic population, potential glycosilation and disulphur formation of enlacing sites. Eighty-eight allergens were identified amongst those in which some biological activity had been reported. The grouping of these according to activity produced the following results: enzymatic (47,2%), enzyme inhibition (11,3%), transport (18,1%), cellular activity regulation (15,9%) and other activities such as conferring resistance to disease on plants and cytolysis (7,9%). In many of these allergens, biological activity has been inferred by their structural homology with known function proteins but the experiments which corroborate the said function have not been carried out. The majority of these allergens have a MW<60 kDa, lp<7.0 and scant olygomer formation in common. Analysis suggested that the capacity to induce allergy is not determined by any of the described biological functions. Even though the cysteinprotease and serin-protease activity of some domestic mites' allergens has been pointed out as being determinant in the said allergens' allergenic role, experimental data is not conclusive and does not allow allergenicity to be attributed to an enzymatic function.