Mucosal-associated invariant T lymphocytes (MAIT lymphocytes) are characterized by two evolutionarily conserved features: an invariant T cell antigen receptor (TCR) alpha-chain and restriction by the major histocompatibility complex (MHC)-related protein MR1. Here we show that MAIT cells were activated by cells infected with various strains of bacteria and yeast, but not cells infected with virus, in both humans and mice. This activation required cognate interaction between the invariant TCR and MR1, which can present a bacteria-derived ligand. In humans, we observed considerably fewer MAIT cells in blood from patients with bacterial infections such as tuberculosis. In the mouse, MAIT cells protected against infection by Mycobacterium abscessus or Escherichia coli. Thus, MAIT cells are evolutionarily conserved innate-like lymphocytes that sense and help fight off microbial infection.

Three hundred and thirty-five patients with high-output enterocutaneous fistulae arising from the small intestine are reported. Median fistula output was 1350 ml/24 h. Eighty-two per cent of patients were referred from other institutions. The fistula opening was associated with evisceration in 165 cases (49 per cent). One or more severity factors were present in 75.5 per cent of the patients. Patients were divided into three groups according to their initial therapy: 21 patients (6 per cent) referred in a moribund state were not operated on (non-intervention); 80 patients (24 per cent) were operated on as an emergency, and the fistula was either exteriorized or defunctioned; 234 patients (70 per cent) were initially managed conservatively. Appropriate local care and nutrition were provided in all cases. Enteral nutrition was the exclusive nutritional support in 285 patients (85 per cent). In 92 cases with proximal fistulae, methods limiting the fistula output or allowing reinfusion of chyme were required. The overall mortality rate was 34 per cent: 100 per cent in the non-intervention group, 55 per cent after emergency surgery, and 19 per cent after conservative treatment. In the latter group, spontaneous closure was obtained in 88 patients (38 per cent). Overall mortality rate was reduced to 19 per cent in patients treated since 1980. Enteral nutrition with appropriate local care may be used in the majority of high-output enterocutaneous fistulae, with an acceptable rate of spontaneous closure. Conservative management is the treatment of choice in the initial period. Emergency surgery should be restricted to the treatment of haemorrhage or intra-abdominal abscesses associated with uncontrolled systemic sepsis.

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