Recruitment of lymphocytes to the human liver

This review discusses the function and localisation of lymphocytes resident within the human liver, under both physiological and pathological conditions. Through description of the mechanisms that mediate lymphocyte recruitment into tissues, this article explains how hepatic endothelial and epithelial cells regulate the recruitment of specific lymphocyte subpopulations. We illustrate that the expression of adhesion molecules and chemokines is crucial to the control of lymphocyte adhesion. Thus, in the normal liver, adhesion molecules such as vascular adhesion protein‐1 (VAP‐1), intercellular adhesion molecule‐1 (ICAM‐1) and intercellular adhesion molecule‐2 (ICAM‐2), and chemokines such as regulated on activation, normal T cell expressed and secreted (RANTES), monocyte chemoattractant protein‐1 (MCP‐1), macrophage inflammatory protein‐1α (MIP‐1α), interferon γ inducible protein‐10 (IP‐10), MIG and interferon inducible T‐cell alpha chemoattractant (ITAC) are involved in lymphocyte binding to different endothelial compartments. However, in response to inflammation or injury, additional expression of adhesion molecules such as VCAM‐1, p‐selectin and e‐selectin, as well as higher levels of chemokines, permits the attraction and retention of specific effector populations of lymphocytes. We also discuss the expression and function of a newly defined adhesion protein, (VAP‐1), and suggest that the unique functions of this protein may provide therapeutic potential for the treatment of liver disease.