[1][2] In humans, MAIT cells are found in the blood, liver, lungs, and mucosa, defending against microbial activity and infection.
[1] The MHC class I-like protein, MR1, is responsible for presenting bacterially-produced vitamin B2 and B9 metabolites to MAIT cells.
[6] In addition to possessing innate-like functions, this T cell subset supports the adaptive immune response and has a memory-like phenotype.
[13] In healthy humans, MAIT cells are found in the lungs, liver, joints, blood, and mucosal tissues, such as the intestinal mucosa.
[13] While MAIT cells display effector characteristics immediately out of the thymus, they may also undergo clonal expansion in the periphery and establish antigen memory.
[1] While protective against some pathogens, MAIT cell activation can produce inflammatory cytokines that augment immunopathology and gastritis in chronic infection by Helicobacter pylori.
[21] Both have been chemically synthesised, stabilised and characterised in the solvent DMSO, allowing for the unstable compounds to be used as reagents for the study of MAIT cells.
[21] A 2017 study also found that some common drugs and drug-like molecules can modulate MAIT cell function in mammals.
[3] MR1 is found intracellularly in the endoplasmic reticulum and interacts with some of the common MHC loading complex components and chaperone proteins (e.g.
[6] MAIT cells display effector-like qualities, allowing them to directly respond to microbial pathogens immediately following activation.
[1] After TCR binding and activation, MAIT cells secrete several cytokines, including tumor necrosis factor alpha (TNF-α), IFN-γ, and IL-17.
These strains avoid MAIT cell-mediated elimination because they have unusual riboflavin metabolic pathways that do not produce viable ligands for MR1 molecules.
[31] After their TCR dependent activation cutaneous MAIT cells initiate support wound repair mechanisms.
One reason for their involvement is their localization which is predominantly near the interface of the dermis and in lesser extend in the epidermis, in close proximity to the basal layer.
[34][35] Even though the gene signature which is descriptive for tissue repair has been repeatedly described, the exact mechanism of the contribution of MAIT to this process cells remains unclear.
The specific gene signature appears to be expressed in MAIT cells for acceleration of the cellular monolayer regrowth after physical damage or other irradiation of the skin.
[7][8] In addition, during periods of myelin degeneration, MAIT cell levels in the peripheral blood have been found to decrease, suggesting their tendency to migrate to sites of MS-related inflammation.
In autoimmune-related inflammatory bowel disease, the immune system initiates a response against healthy parts of the gastrointestinal tract, such as the mucosal microbiome.
[7] In systematic autoimmune rheumatic diseases, such as rheumatoid arthritis and systemic lupus erythematosus (SLE), MAIT cells are activated through TCR-independent signaling.
[7][18] In this way, MAIT cells facilitate and intensify the harmful effects of systematic autoimmune rheumatic diseases.