Role of MAIT cells in the immunopathogenesis of inflammatory diseases: New players in old game

Abstract

Current advances in immunology have led to the identification of a population of novel innate immune T cells, called mucosa-associated invariant T (MAIT) cells. The cells in humans express an invariant TCRα chain (Vα7.2-Jα33) paired with a limited subset of TCRβ chains (Vβ2, 13 and 22), are restricted by the MHC class I (MH1)-related (MR)-1, and recognize molecules that are produced in the bacterial riboflavin (vitamin B2) biosynthetic pathway. They are present in the circulation, liver and at various mucosal sites (i.e. intestine, lungs and female reproductive tract, etc.). They kill host cells infected with bacteria and yeast, and secrete soluble mediators such as TNF-α, IFN-γ, IL-17, etc. The cells regulate immune responses and inflammation associated with a wide spectrum of acute and chronic diseases in humans. Since their discovery in 1993, significant advances have been made in understanding biology of MAIT cells and the potential role of these cells in the pathogenesis of autoimmune, inflammatory and infectious diseases as well as cancer in humans. The purpose of this review is to provide a current state of our knowledge about MAIT cell biology and delineate their role in autoimmune and inflammatory diseases (sterile or caused by infectious agents) and cancer in humans. A better understanding of the role of MAIT cells in human diseases may lead to novel ways of immunotherapies.

Toll-like receptors in immunity and inflammatory diseases: Past, present, and future

“…monocytes/macrophages, neutrophils, dendritic cells (DCs), natural killer (NK) cells, mast cells (MCs), eosinophils, basophils along with newly identified innate lymphoid cells (ILCs) and mucosal associated invariant T (MAIT) cells, γδT cells, NKT cells etc.) [3][4][5][6][7][8][9] and its humoral components that is circulating complement system proteins/components, cytokines and chemokines secreted by innate immune cells along with various antimicrobial peptides (AMPs) (i.e. LL37, Bactericidal/permeability increasing protein (BPI) etc.…”

The Role of CD1d and MR1 Restricted T Cells in the Liver

“…Distribution of MAIT cells differs between humans and mice. The frequency of MAIT cells in C57BL/6 mice accounts for ~0.1% of the peripheral T cell population ( 49 ), whereas 1–10% of them are identified in human peripheral blood. Moreover, the occurrence of MAIT cells varies widely among tissues in healthy adults, ranging from 2% (ileum) to 60% (jejunum), and they can make up ~20–50% of intrahepatic T cells.…”

Macrophages: The Potent Immunoregulatory Innate Immune Cells

“…The innate immune cells comprise of epithelial cells, endothelial cells (ECs), the granulocytes (i.e. neutrophils, basophils, eosinophils, and mast cells (MCs), monocytes, macrophages, natural killer (NK) cells, dendritic cells (DCs), invariant NKT cells (iNKT cells), γδT cells, and newly described innate immune T cells called mucosal invariant T cells (MAIT) cells and innate lymphoid cells (ILCs) [1][2][3][4][5][6][7][8][9] (Figure 1). These innate immune cells are crucial to maintain the immune homeostasis and regulate adaptive immune system via acting as antigen presenting cells (APCs) along with providing other signaling molecules/factors required in the effective adaptive immune response in response to infection or other sterile chronic inflammatory diseases including, allergy, autoimmunity, cancer, and metabolic diseases including type 1 diabetes mellitus (T1DM), and obesity etc.…”