Interleukin (IL) 15 production after gluten challenge. Representative IL15 western blot of (A) whole biopsy protein extract of a responding patient with coeliac disease (CD) on gluten‐free diet (GFD) challenged with gliadin compared with basal culture, and two patients without CD challenged with gliadin and the synthetic gliadin peptides 19‐mer and deaminated 33‐mer, respectively, compared with the basal culture. Interestingly, none of the basal cultures produced this cytokine. (B) 24 h culture supernatant (SN) of a patient without CD basal culture and the 3 and 24 h culture supernatants of the same patient after challenge with the 19‐mer and deaminated 33‐mer, respectively. IL15, positive control lane.