Abstract
A stable clonal cell line of human neural stem cells (NSCs), HB1.F3, has been shown therapeutic effect on acute stroke or intracerebral haemorrhage by the mechanisms of cell replacement and several bystander effects. To investigate the bystander immunomodulatory functions of HB1.F3 cells, we examined immunosuppressive effects of HB1.F3 on T cell effector functions in vitro. We found that heat-labile soluble factors from hNSCs culture supernatant are attributed to the inhibition of peripheral blood lymphocytes (PBLs) proliferation induced by mixed lymphocyte reaction (MLR) or phorbol myristate acetate (PMA)/ionomycin. In contrast to inhibitory effect of HB1.F3, they promoted cytokine secretion from PBLs including IFN-r, TNF-a, IL-10, IL-6 during mixed lymphocyte reaction by soluble factor dependant-manner. HB1.F3 cell line expressed TGF-beta and Trail mRNA, not FasL. we confirmed that the apoptosis induction of PBLs by HB1.F3 is one of the mechanisms of T cell proliferation inhibition during MLRs. In summary, HB1.F3 cells could suppress the T cell proliferation by induction of apoptosis and promote both inflammatory and immune suppressive cytokines. This study suggested that therapeutically effective hNSCs cell line on several stroke models might be due to the bystander immunomodulatory functions by the secretion of immunosuppressive soluble factors.
