Mechanisms of Allergy
The IL1A genotype associates with atopy in nonasthmatic adults,☆☆

https://doi.org/10.1067/mai.2002.126784Get rights and content

Abstract

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-1α (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 22 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, ≥1 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. (J Allergy Clin Immunol 2002;110:429-34.)

Section snippets

Methods

Asthmatic patients and control subjects were participants in a Finnish population-based case-control study aimed at identifying risk factors and predictors of the outcome of adult asthma. Inclusion criteria for asthmatic subjects were age over 30 years and entitlement to special reimbursement for asthma medication from the Social Insurance Institution of Finland. The entitlement is granted if the criteria for persistent asthma are fulfilled, as certified by a chest specialist. Typical history,

Skin prick testing

In the asthmatic group there were more subjects with positive skin test responses among the female population than among the male population (62.0% vs 47.3%; P = .025, χ2 testing, df = 1). However, the number of positive skin test reactions was similar in patients of both sexes. In the control group the percentage of subjects with positive skin test responses was 38.9% in female subjects and 37.3% in male subjects (P = .756, χ2 testing, df = 1). As in the case of asthmatic patients, no

IL1A genotype

The IL1A genotype distribution was similar in the asthmatic and control groups (Table III). This was also the case when the sexes were analyzed separately (data not shown).

There was no significant association between IL1A genotype and skin test results in asthmatic patients. In the control subjects, on the other hand, the data obtained showed that the IL1A genotype distribution was significantly different between the individuals with positive (≥1 positive reactions) and negative skin test

Discussion

Our study was conducted to assess 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. We have previously shown that the IL1B gene carries asthma susceptibility in male subjects.10 The IL1A genotype distribution in the asthmatic and control groups was similar, and therefore no contribution to asthma susceptibility was observed.

As expected, atopy was more common among asthmatic

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    Supported by Rehabilitation Funds of the Finnish Social Insurance Institution, the Medical Research Fund of Tampere University Hospital, and the Tampere Tuberculosis Foundation.

    ☆☆

    Reprint requests: Jussi Karjalainen, MD, University of Tampere, Medical School, FIN-33014 University of Tampere, Finland.

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