Alteration in immune function in patients with fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a disease spectrum that spans simple steatosis, fibrosis, and ultimately cirrhosis, and is a leading cause of chronic liver disease globally. The severe variant of NAFLD, non-alcoholic steatohepatitis (NASH), is characterized by triglyceride accumulation within hepatocytes and the subsequent inflammatory pathway activation, ultimately progressing to cirrhosis in 10%-20% of patients. NASH is a known major risk factor for the development of hepatocellular carcinoma (HCC), and there is emerging data demonstrating the impact of NASH on immune subsets and the tumor microenvironment that may influence therapeutic response. This review describes the various ways in which the immune system is altered in patients with NASH. The innate immune system in NASH shows alterations in dendritic and Kupffer cells, impaired cytotoxicity of Natural Killer cells, and an accumulation of neutrophils. Additionally, there is emerging evidence emphasizing the role of the adaptive immune system in the development and progression of NASH, seen in the alteration of B-cells, T-cells, and NKT Cells. Due to the complex interplay of the immune system in NAFLD/NASH and its progression to HCC, many current treatments focus on targeting immune cells for HCC therapy. Recently, immune checkpoint inhibitors such as atezolizumab and bevacizumab have been approved as first-line therapy for unresectable HCC. Although an emerging field of research, further studies and clinical trials are needed to understand the complex interface of NASH, HCC and the immune response.