Background: IL-1 receptor-like 1 (IL1RL1) is a membrane receptor involved in TH2 inflammatory responses and eosinophilia. Single nucleotide polymorphisms (SNPs) in IL1RL1 have been associated with blood eosinophil counts in a genome-wide association study and with asthma in family-based and case-control studies. Objective: We assessed in the prospective birth cohort Prevention and Incidence of Asthma and Mite Allergy (PIAMA) whether IL1RL1 SNPs associate with levels of its soluble transcript IL1RL1 (IL1RL1-a) in serum, blood eosinophil counts, and asthma prevalence from birth to age 8 years, and whether IL1RL1-a serum levels associate with blood eosinophil counts. Methods: Fifteen IL1RL1 SNPs were genotyped. Serum IL1RL1-a levels were measured in 2 independent subsets within PIAMA, at 4 and 8 years. Blood eosinophil counts were measured in 4-year-old children. Results: In 2 independent subsets of children, 13 of 15 SNPs were associated with serum IL1RL1-a levels at ages 4 and 8 years with a consistent direction of effect for each allele. Rs11685480 allele A and rs1420102 allele A were significantly associated with lower numbers of blood eosinophils. In the total cohort, rs1041973 allele A was associated with a decreased risk of developing asthma (odds ratio, 0.70; 95% CI, 0.54-0.90). Rs1420101, recently identified in a genome-wide association study in the Icelandic population, was not associated with asthma in this study. IL1RL1-a levels were not associated with eosinophil counts. Conclusion: We demonstrate that IL1RL1 polymorphisms are associated with serum IL1RL1-a, blood eosinophils, and asthma in childhood.

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Keywords IL1RL1, IL1RL1-a, asthma, atopy, children, eosinophils
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Savenije, O.E, Kerkhof, M, Reijmerink, N.E, Brunekreef, B, de Jongste, J.C, Smit, H.A, … Koppelman, G.H. (2011). Interleukin-1 receptor-like 1 polymorphisms are associated with serum IL1RL1-a, eosinophils, and asthma in childhood. Journal of Allergy and Clinical Immunology, 127(3), 750–756. doi:10.1016/j.jaci.2010.12.014