To assess whether IL-9 may contribute to allergy in CF patients, we determined the effect of the non-synonymous IL9 p.Thr117Met (c.350C>T, rs2069885) polymorphism, known to be associated with lung function and sensitization36, 37 on total and Aspergillus-specific IgE levels in CF patients (Supplementary Table 1). This evidence concerns the gene IL9 and cystic fibrosis.