Incorporating mucosal-associated invariant T cells into the pathogenesis of chronic liver disease

Table 5 Mucosal-associated invariant T cells in cholestatic liver disease and decompensated cirrhosis

Liver disease	MAIT cell features	Clinical implications
PBC	Circulating MAIT cells decreased[54,55]; Intrahepatic MAIT cells variable[54,55]; Upregulated liver-homing CXCR6, CCR6[54]; Aberrant MAIT cell function[55]; Depletion associated with increased AP[55]; Low IFN-γ unable to impair HSC activation[55]; Preferential portal tract distribution[55]; Activation associated with increased ALT[54]; Cholic acid-induced hepatocyte IL-7[55]; IL-7-induced pro-inflammatory cytokines[55]; Limited expression of IL-7R and IL-18R[54]	Immune exhaustion[54,55]; Apoptosis-based depletion (AICD)[54,55]; Unable to prevent cholestasis[54,55]; Unable to inhibit hepatic fibrosis[55]; Defective barrier to gut-derived ligands[55]; Pro-inflammatory cytokine milieu[54,55]; UDCA improves but not restorative[54,55]; Presumed defective protective role[54,55]; Presumed active pathogenic role[54,55]
PSC	Circulating MAIT cell frequency reduced[57]; Intrahepatic MAIT cell frequency less[56]; CD69, CD56, PD-1, and CD39 expressed[57]; Impaired response to bacteria[57]; Abundant extrahepatic bile duct MAIT cells[57]	Activated and immune exhausted[57]; Depleted in circulation and liver tissue[56,57]; Less anti-bacterial protection[57]; Abundant migration to bile ducts[57]; Presumed defective protective role[57]
Decompensated cirrhosis	Circulating MAIT cell frequency reduced[58]; High expression of activation markers[58]; MAIT cell frequency increased in ascites[58]; Increased cytokines from peritoneal cells[58]; Increased granzyme B from peritoneal cells[58]; Increased frequency in SBP ascites[58]; Homing chemokine CXCR3 on MAIT cells[58]; Abundant CXCL10 ligand in ascites[58]	Activated and recruited to ascites[58]; Anti-microbial protective response[58]; Protective role of uncertain efficacy[58]

AICD: Activation-induced cell death; ALT: Serum alanine aminotransferase level; AP: Serum alkaline phosphatase level; HSC: Hepatic stellate cells; IFN-γ: Interferon-gamma; IL-7: Interleukin 7; IL-7R: Interleukin 7 receptor; IL-18R: Interleukin 18 receptor; MAIT: Mucosal-associated invariant T; PBC: Primary biliary cholangitis; PD-1: Programmed cell death 1; PSC: Primary sclerosing cholangitis; SBP: Spontaneous bacterial peritonitis; UDCA: Ursodeoxycholic acid.