Non-alcoholic fatty liver disease (NAFLD) involves numerous disease states described by hepatic steatosis and is significantly linked to obesity and metabolic syndrome. 

On the other hand, Non-alcoholic steatohepatitis (NASH) also involves inflammatory changes and hepatocellular damage describing a more severe condition. Treatment for NASH still demands more research. 

The immune system plays a crucial role in NAFLD progression and other obesity-related comorbidities, with both the innate and adaptive immune system getting involved. T cells make the cellular component of the adaptive immune system. It has many differentially active subsets like T helper (Th) cells, regulatory T (Treg) cells, and cytotoxic T (Tc) cells, along with several innate T-cell subsets. 

Th1, Th2, Th17, and Th22 cells have been shown to decrease adiposity. Th2, Th22, and Treg cells are involved in attenuating insulin resistance, while Th1, Th17, and Tc cells have a provoking effect. 

Regarding NAFLD, Th22 and Treg cells have demonstrated an overall tempering effect, while Th17 and Tc cells may induce more liver damage and fibrosis progression. 

The evidence regarding the role of the innate T-cell subsets warrants further exploration.

Source: Van Herck MA, Weyler J, Kwanten WJ, Dirinck EL, De Winter BY, Francque SM and Vonghia L (2019) The Differential Roles of T Cells in Non-alcoholic Fatty Liver Disease and Obesity. Front. Immunol. 10:82. doi: 10.3389/fimmu.2019.00082