**4. Tolerogenic properties of liver cells**

Hepatic cells represent a heterogeneous population where different liver residents have their own tolerogenic approach (**Figure 2**).

#### **4.1 Hepatocytes**

Parenchymal hepatocytes are the major population in the liver. Although being involved in metabolism, toxin neutralization and glycogen synthesis, they function also as immune cells by expressing immune-associated molecules like pattern recognition receptors (PRRs), adhesion and major histocompatibility complex (MHC) molecules [30, 31]. The latter permit hepatocytes to act as antigen-presenting cells for CD8+ T cells and to trigger their activation and proliferation [32]. However, the particular hepatic environment does not ensure the required survival factors

*Regulatory T Cells in the Mosaic of Liver Transplantation Tolerance DOI: http://dx.doi.org/10.5772/intechopen.94362*


#### **Figure 2.**

*The mosaic of tolerogenic cells in the liver. On the table below are shown main tolerogenic mechanisms, employed by every population.*

for CD8+ cells and they rapidly undergo activation-induced apoptosis [33]. Interestingly, the inflammatory response can be accompanied by the expression of MHC class II molecules followed by antigen presentation to CD4+ T cells [34, 35]. Depending on the differentiation status of helper cells, they may undergo Th2 differentiation of uncommitted CD4 T cells, or abrogated ability of previously differentiated Th1 to secrete interferon-γ**,** and finally - switch of CD4 + T effector cells towards induced regulatory T cells (FoxP3 + CD25+) [33, 36] . Ergo, liver parenchymal cells have substantial tolerogenic potential directed to both CD4+ and CD8+ T cells. Whether all would be launch together or not need to be elucidated.
