**4.5 Liver dendritic cells**

Dendritic cells (DCs) are professional antigen-presenting cells. Following the antigen processing, they activate T cells and unlock the adaptive immune reaction. The liver-resident DCs are distinct population as compared to blood DCs. While DCs expressing CD1c and CD14 represent 95% of blood DCs, in liver they are 70% *Regulatory T Cells in the Mosaic of Liver Transplantation Tolerance DOI: http://dx.doi.org/10.5772/intechopen.94362*

and those expressing CD141 increase up to 30% [53]. It is still unclear in details how these cells contribute to the development of immune tolerance. Although some evidences that DCs may enhance graft rejection by increase of CD80 and CD86 expression [54, 55], the depletion of donor DCs is followed by graft rejection [56]. The investigations of Bamboat et al. demonstrate that liver DCs generate more suppressive CD4<sup>+</sup> CD25<sup>+</sup> FoxP3+ T regulatory cells and IL-4-producing Th2 cells via an IL-10-dependent mechanism [57]. Another particular feature of LDCs is their low endocytosis capacity and weak capacity to stimulate T cells. Conversely, they produce high levels of the immunosuppressive IL-10 [58, 59]. The comparison with their splenic match reveal important differences: lower secretion of type I interferons, "lipid-based dichotomy" – lipid contents dependent antigen presentation, plasmacytoid DC (B220<sup>+</sup> ) account for 19% of liver DC, but only 5% of spleen DC [60–62].
