The IL1A genotype associates with atopy in nonasthmatic adults

Background: The skin prick test is used to examine specific IgE-mediated allergic responses. Generally, results accord well with anamnestic information on atopy. Several genetic factors probably affect the strength of allergen-mediated skin test reactions. Objective: We sought to investigate skin test findings in a population-based sample of adult asthmatic patients and control subjects and to establish whether the IL1A genotype affects allergy testing. Methods: We analyzed the single G-to-T base exchange polymorphism in exon 5 at +4845 of the gene encoding IL-1alpha (IL1A) in adult asthmatic patients (n = 245) and nonasthmatic control subjects (n = 405). The data were assessed for correlation with data on the skin test responses of these subjects to common allergens. Results: The IL1A genotype distribution and allele frequencies proved similar in patients and control subjects. Surprisingly, the IL1A genotype distribution was markedly different in control subjects with positive (ie, A positive reaction) and negative skin test responses (P=.006). This difference was caused by an increase in the frequency of the rarer allele 2 in control subjects with negative skin test responses (P=.004). Conclusion: Our study demonstrates that the IL1 gene complex is involved in the regulation of IgE-mediated atopic reactions. The results suggest that skin test responses to specific allergens are differently regulated in nonasthmatic and asthmatic subjects. Because of the potential role of the IL1A genotype as a confounding factor in skin prick testing, these results, require special attention and should be further evaluated in other clinical settings.