Immune Mechanisms in Fatty Liver Disease

Fatty liver disease, encompassing both alcoholic and non-alcoholic forms, arises from a complex interplay between metabolic stress and immune activation. Hepatocytes under lipid overload release danger signals that engage resident Kupffer cells and liver sinusoidal endothelial cells, triggering the recruitment of circulating monocytes, neutrophils and lymphocytes. These innate immune cells generate cytokines, chemokines and reactive oxygen species, which not only drive inflammation but also activate hepatic stellate cells to deposit extracellular matrix and promote fibrosis. Adaptive immunity further shapes disease progression: CD4+ T helper cells orchestrate pro-inflammatory or regulatory responses, while cytotoxic CD8+ T cells and tissue-resident lymphocytes contribute to both injury and repair. Crosstalk with the gut microbiota via microbial metabolites and endotoxins amplifies hepatic inflammation, establishing a gut–liver axis that influences disease severity. Conversely, specialised immune subsets can foster resolution, inducing apoptosis of activated stellate cells and restoring tissue homeostasis. Understanding these interwoven mechanisms is essential for developing targeted therapies to arrest inflammation, reverse fibrosis and improve clinical outcomes.

Research from Nature Portfolio

Recent studies have uncovered a pivotal role for liver-resident memory CD8+ T cells in driving the resolution of fibrosis. In a dietary model of non-alcoholic steatohepatitis (NASH), enrichment of CD69+CD103–CD8+ tissue-resident memory cells was associated with fibrosis regression. These cells rely on interleukin-15 for maintenance and employ CCR5-mediated homing to engage activated hepatic stellate cells. By expressing Fas ligand, they selectively induce apoptosis in pro-fibrogenic stellate cells, thereby promoting matrix remodelling and restoring hepatic architecture. The presence of similar cells in fibrotic regions of human livers further underscores their therapeutic potential as a cellular target for fibrosis resolution.

Immune Mechanisms in Fatty Liver Disease publication trend

The graph below shows the total number of articles in immune mechanisms in fatty liver disease across all publications each year (not limited to Nature Index journals).

Technical terms

Kupffer cells: Liver-resident macrophages that sense danger signals and orchestrate inflammatory responses.

Hepatic stellate cells (HSCs): Perivascular cells that transform into collagen-producing myofibroblasts upon activation.

Tissue-resident memory T cells (Trm): Long-lived CD8+ lymphocytes that persist in tissues and mediate local immune responses.

Fas ligand (FasL): A cell-surface molecule that induces apoptosis in target cells expressing the Fas receptor.

Gut–liver axis: The bidirectional communication network between intestinal microbiota and liver immunity.

References

1. Invited review liver fibrosis in NAFLD/NASH: From pathophysiology towards diagnostic and therapeutic strategies. Molecular Aspects of Medicine (2023).
2. Prophylactic treatment with Bacteroides uniformis and Bifidobacterium bifidum counteracts hepatic NK cell immune tolerance in nonalcoholic steatohepatitis induced by high fat diet. Gut Microbes (2024).
3. CD8+ tissue-resident memory T cells promote liver fibrosis resolution by inducing apoptosis of hepatic stellate cells. Nature Communications (2021).