Hepatic environment elicits monocyte differentiation into a dendritic cell subset directing Th2 response.

Background/aims: Dendritic cells (DCs), which play a critical role during immune response, could present alternative differentiation patterns depending on tissue microenvironment. Our aim was to examine the influence of hepatic microenvironment on human monocyte differentiation into DCs.
Methods: Cytology, immunophenotyping, cytokine production and T-cell activation were analyzed in DCs differentiated from human monocytes co-cultured with rat liver epithelial cells (RLEC) or human cells from various tissue origins and compared to control DCs obtained on plastic with GM-CSF/IL-4.
Results: RLEC environment promotes DC differentiation in the presence of IL-4 without GM-CSF. These DCs evidence similar expression of MHC-II, co-stimulatory and adhesion molecules than control DCs, but distinct lineage markers defining a CD11c+/CD14+/CD123+ DC subset. This phenotype is common to DCs from RLEC and human liver environment and differs from that obtained with skin or intestine environments. Functionally, they produce IL-10 but not IL-12p70 and favor IL-4/IL-10 secretion by T-cells rather than IFN-gamma.
Conclusions: Our results confirm that tissue niches modulate DC differentiation and demonstrate that hepatic environment influences monocyte differentiation into a DC subset directing Th2 response, a key data for understanding the specialized immune response in liver. They also make RLEC co-culture system useful for studying liver DC functions.