For example, elastase-like activity of the pathogen Pseudomonas aeruginosa can lead to the production of peptides following gluten metabolism with increased immunogenicity in celiac disease (CeD) patients,18 and serine proteases from a consortium of gut bacteria modulate the excitability of nociceptors via activation of protease-activated receptor 4 (PAR-4).19 However, the mechanistic characterization of specific bacterial products such as proteases in gut disorders still represent an enormous challenge. This evidence concerns the gene F2RL3 and celiac disease.