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

Table 2 Mucosal-associated invariant T cell demographics and clinical implications

Feature	Demographics	Clinical implications
Frequency (based on percentage of CD3+ T cells)	Circulation, 0.1%-10%[11,61,81,131]; Intestine, 2%-20%[11,61,102,132]; Lung, 1%-10%[11,15,61,81]; Liver, 10%-40%[11,43,61,82,133]; Lymph nodes, < 1%[11,61]	Liver is most MAIT cell enriched tissue[61]; MAIT cells can react with microbial antigens and metabolites in portal circulation and in bile[133]
Hepatic distribution	Present in bile ducts, portal tracts, sinusoids[55,133]; Chemokine-directed migrations[77]; CCR6, CXCR6, integrin αEβ7 to bile ducts[77,133]; CXCR3, LFA-1, VLA-4 to sinusoids[77,133]	Nature of the liver disease may direct MAIT cell migration to key site of inflammation[77,133,134]
Age-related changes	Numbers in blood increase up to age 40 yr[135]; Numbers in blood decline after age 60 yr[135]; MAIT cell apoptosis increases with age[135]; Depletion nadir after age 80 yr[136]; Depletion may be faster in men than women[131]; Shift from CD8+ to CD4+ cells with aging[131,137]; May be less pro-inflammatory with aging[131]	Ethnic and environmental factors possible[135]; Uncertain effect on severity and outcome[136]; Consider in design of clinical investigations

LFA-1: Lymphocyte function-associated-1 protein; MAIT: Mucosal-associated invariant T cell; VLA-4: Very late antigen 4.