ARPP21 and cystic fibrosis: Since all the genes of interest are located on pathogenicity islands, and the phenotypes to which they contribute to are often seen in variants isolated from the lungs of CF patients, we strongly believe that deciphering the central role of the Rcs/Pvr system in this process and characterizing the stimuli that activate these pathways is a major issue in the understanding and treatment of disease associated with chronic P. aeruginosa infection.