Haplotypes of the interleukin-4 receptor α chain gene associate with susceptibility to and severity of atopic asthma

Summary Background Development of asthma is likely to depend on a complex interaction between environmental and genetic factors. Several groups have suggested the gene of the IL‐4 receptor α chain (IL4R) as a candidate gene for the development of asthma, although association with single polymorphisms has shown contradicting results. Objective We chose to analyse IL4R gene haplotypes and assess their possible relevance in susceptibility to asthma and to certain clinical phenotypes. Methods IL4R gene haplotypes were analysed, based on the three markers C‐3223T, Q551R and I50V, using the expectation–maximization algorithm, in 170 atopic asthma patients and 350 controls, all adult Swedish Caucasians. Results Our data showed significantly higher levels of soluble IL‐4R (sIL‐4R) in asthma patients compared with controls (P