T cells play an important role to build up an effective immune response and are essential in the eradication of pathogens. To establish a long-lasting protection even after a re-challenge with the same pathogen, some T cells differentiate into memory T cells. Recently, a certain subpopulation of memory T cells at different tissue-sites of
infection was detected-tissue-resident memory T cells (TRM cells). These cells can patrol in the tissue in order to encounter their cognate
antigen to establish an effective protection against
secondary infection. The liver as an immunogenic organ is exposed to a variety of pathogens entering the liver through the systemic blood circulation or via the portal vein from the gut. It could be shown that intrahepatic TRM cells can reside within the liver tissue for several years. Interestingly, hepatic TRM cell differentiation requires a distinct
cytokine milieu. In addition, TRM cells express specific surface markers and
transcription factors, which allow their identification delimited from their circulating counterparts. It could be demonstrated that liver TRM cells play a particular role in many
liver diseases such as
hepatitis B and C
infection,
non-alcoholic fatty liver disease and even play a role in the development of
hepatocellular carcinoma and in building long-lasting immune responses after vaccination. A better understanding of intrahepatic TRM cells is critical to understand the pathophysiology of many
liver diseases and to identify new potential
drug targets for the development of novel treatment strategies.