Antimicrobial activity of mucosal-associated invariant T cells.

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.

MAIT cells detect and efficiently lyse bacterially-infected epithelial cells.

Mucosal associated invariant T cells (MAIT) are innate T lymphocytes that detect a large variety of bacteria and yeasts. This recognition depends on the detection of microbial compounds presented by the evolutionarily conserved major-histocompatibility-complex (MHC) class I molecule, MR1. Here we show that MAIT cells display cytotoxic activity towards MR1 overexpressing non-hematopoietic cells cocultured with bacteria. The NK receptor, CD161, highly expressed by MAIT cells, modulated the cytokine but not the cytotoxic response triggered by bacteria infected cells. MAIT cells are also activated by and kill epithelial cells expressing endogenous levels of MRI after infection with the invasive bacteria Shigella flexneri. In contrast, MAIT cells were not activated by epithelial cells infected by Salmonella enterica Typhimurium. Finally, MAIT cells are activated in human volunteers receiving an attenuated strain of Shigella dysenteriae-1 tested as a potential vaccine. Thus, in humans, MAIT cells are the most abundant T cell subset able to detect and kill bacteria infected cells.

Traumatic Patellar Tendon Rupture Repair Using Synthetic Ligament Augmentation.

Rupture of the patellar tendon is an infrequent pathology, and surgical repair with nonabsorbable sutures is the gold standard for management. Many surgeons augment the repair using one of many proposed methods: cerclage wires, Dall-Miles cables, autologous hamstring grafts, and tendon allografts. In this study, we propose the augmentation of patellar tendon repair using an artificial ligament. The questions to be assessed in this study are as follows: (1) measurement of functional results 1 year after surgery using the Lysholm score and (2) the incidence of both rerupture, and surgical complications within the first year postsurgery, the median knee range of motion at 3 months and 1-year postsurgery, patient satisfaction, and postsurgery patellar height, measured using the Caton-Deschamps Index. In our center, we performed 30 suture repairs of traumatic patellar tendon ruptures between 2015 and 2016. Tendon repair was always augmented using an artificial ligament (LT60, Orthomed). The results were evaluated 1 year after surgery. The 1-year postsurgery median Lysholm score was 96 (first quartile-third quartile [Q1-Q3]: 95-100). None of the following complications were reported: second surgery for any reason, new rupture, and superficial or deep infection. Radiological analysis showed a median Caton Index of 1 (Q1-Q3: 0.9-1) postsurgery. Excellent Lysholm scores were observed 1 year after synthetic ligament augmentation of patellar tendon sutures, with a low rate of complications compared with published studies.