The R576 IL-4 receptor alpha allele correlates with asthma severity

Background: Atopic disorders, including asthma, are very prevalent affectin g up to 40% of populations, and their incidence is on the rise Although env ironmental factors are important in the development of atopy, there is a st rong genetic predisposition. Several genes and chromosomal regions have bee n linked to atopy and asthma, supporting the polygenic nature of these diso rders. IL-4 and IL-13 are T(H)2 cytokines with numerous activities that con tribute to allergic inflammation and asthma, Both IL-4 and IL-13 use the IL -4 receptor a chain (IL-4R alpha) as a component of their respective recept or systems. Allelic variants of IL-4R alpha have been reported, and the R57 6IL-4R alpha allele was recently shown to be a risk factor for atopy: Objective: We sought to determine whether the R576 allele was associated wi th the prevalence or clinical severity of asthma. Methods: We developed a rapid, reliable, PCR-based assay to screen individu als for the R576IL-4R alpha allele and used this assay to genotype prospect ively recruited individuals with asthma (n = 149) and control subjects (n = 57), Results: There was a strong association of R576IL-4R alpha with the prevale nce and clinical severity of asthma. in a prospective cohort, homozygosity for R576 was significantly increased in individuals nith asthma (0 = 149, P = .03; relative risk 8.2) compared with controls (n = 57). Furthermore, 1 or 2 copies R576IL-4R alpha correlated with asthma severity establishing a genotype-phenotype relationship and suggesting a gene dosage effect Conclusions: Thus R576IL-4R alpha acts as an allergic asthma susceptibility and disease-modifying gene and may serve as a clinically useful marker of asthma severity.