[The liver as an immunological organ].

In many species, liver transplants induce antigen-specific immunological tolerance. Furthermore, the liver seems to play an important role in oral tolerance although the exact mechanisms as to how the liver induces immunological tolerance still need to be defined. Apart from the presence of an unusual subset of effector cells of the innate immune system, the liver is rich in CD 8+ T cells with an activated and preapoptotic phenotype. In this article, we discuss the suggested hypothesis to explain this phenotype. In addition, we discuss the different cell types that have been suggested to serve as antigen-presenting cells (APC) for naïve T cells. Interestingly, different APCs seem to use different mechanisms to induce tolerance while hepatic stellate cells were reported to induce an effective immune response. © Georg Thieme Verlag KG Stuttgart · New York.