Reference values for IgG and IgG4 serum levels specific for inhalant allergens in non-atopic subjects.

The IgG response to allergens is well-known, however few studies have investigated IgG and IgG4 production in normal subjects. Therefore, total IgG and IgG4 serum levels specific for 6 common inhalant allergens were measured in 282 non-allergic subjects to establish reference values at different ages and sex. Thus, 282 subjects were studied (141 female and 141 male) ranging from pre-school to adult age, all living in Northern Italy at the time of the study. Family history of first degree relatives and personal history were negative for allergic diseases. The findings obtained in this study indicate that: i) reference values for specific IgG4 and IgG levels against the allergen studied should take into account both the sex and age of the subject evaluated; ii) there is a difference in trend for age between seasonal and perennial allergens and iii) the relationships between age and specific IgG4 and IgG levels have different slopes. In conclusion, relevant differences exist in the distribution of IgG and IgG4 levels in normal subjects.