The T cells infiltrating the pancreas in CF patients secrete proinflammatory cytokines, known to inhibit insulin secretion [reviewed in (140)] Proinflammatory T cells in CF may thus contribute to CFRD by producing cytokines that increase the level of systemic inflammation, by infiltrating islets, and by destroying pancreatic β-cells, as well as by inhibiting insulin production by producing cytokines in the vicinity of β-cells. This evidence concerns the gene INS and cystic fibrosis.