Interactions between hepatic stellate cells and the immune system

Stellate cells and immune cells are both active participants in the pathoge nesis of liver disease. Interactions between these two populations are impo rtant determinants of disease outcome. Kupffer cells, neutrophils, and lymp hocytes all have the potential to influence stellate cells. They produce a host of humoral mediators, including oxidants, nitric oxide, cytokines, eic osanoids, and proteinases, which can affect stellate cell proliferation, ge ne expression, and contractility. One important feature of stellate cell-im mune cell interactions is that they are bidirectional. Not only do stellate cells receive signals from leukocytes, but they also elaborate signals tha t target leukocytes. Specifically, stellate cells can promote leukocyte che motaxis and adherence, and they may also influence leukocyte activation by producing regulatory cytokines. Studies in culture provide an important bac kground for understanding the effects of specific mediators on stellate cel ls and immune cells. Experiments in vivo offer an important adjunct, but of ten lead to confounding effects that limit interpretation. Both types of st udies are required to develop a better understanding of the complex interpl ay between stellate cells and leukocytes.