Intestinal Inflammation and Dysregulated Immunity in Patients with Inherited Caspase-8 Deficiency.

Caspase-8 (CASP8) is a protease that initiates apoptosis and regulates inflammation and immune responses. We identified germline mutations in CASP8 in 3 unrelated patients with infant-onset inflammatory bowel disease: 2 patients were homozygous for the mutation 710A>G, p.Q237R, which resulted in reduced protein expression, and 1 patient carried the mutation 793C>T, p.R265W. We isolated peripheral blood mononuclear cells from our index patient and observed defects in T- and B-cell maturation, proliferation, and/or activation. Macrophages from 1 patient with CASP8 deficiency and monocytic BLaER1 cells with knockout of CASP8 or overexpression of CASP8 with the 710A>G mutation had altered inflammasome activity upon stimulation with lipopolysaccharide. Patient-derived intestinal organoids and colon carcinoma cells with knockout of CASP8 had defects in cell death processes that involved loss of TRAIL signaling and increased necroptosis. These findings indicate that CASP8 controls inflammation, innate and adaptive immunity, and intestinal barrier integrity in humans.