Suppression of T-cell proliferation by and B7-H1 expression on human liver-derived stem cells.

Background: Many types of stem cells have been widely used for the treatment of liver diseases. The therapeutic effect of stem cells is predominantly based on the immune regulatory properties of these cells.

Methods: We isolated human liver stem cells (HLSCs), which are considered intrahepatic stem cells, and examined their suppression of T-cell proliferation induced by phytohemagglutinin.

Results: HLSCs inhibited phytohemagglutinin-induced T-cell proliferation not only in direct co-culture but also in indirect co-culture in a cell number-dependent manner. That is, T-cell proliferation was substantially inhibited by cell-to-cell contact regardless of soluble factor(s). B7-H1, a co-inhibitory molecule that relies on cell-to-cell contact, was found to be constitutively expressed at low levels on HLSCs. Furthermore, its expression was upregulated moderately by tumor necrosis factor-α and dramatically by interferon-γ.

Conclusions: These results suggest that HLSCs would have therapeutic effects through T-cell suppression in acute liver diseases.