Human Parthenogenetic Embryonic Stem Cell-Derived Neural Stem Cells Express HLA-G and Show Unique Resistance to NK Cell-Mediated Killing

Jessica Schmitt, Sigrid Eckardt, Paul G. Schlegel, Anna-Leena Sirén, Valentin S. Bruttel, K. John McLaughlin, Jörg Wischhusen, Albrecht M. Müller

Parent-of-origin imprints have been implicated in the regulation of neural differentiation and brain development. Previously we have shown that, despite the lack of a paternal genome, human parthenogenetic (PG) embryonic stem cells (hESCs) can form proliferating neural stem cells (NSCs) that are capable of differentiation into physiologically functional neurons while maintaining allele-specific expression of imprinted genes. Since normal hESC-derived NSCs (N NSCs) are targeted by immune cells, we characterized the immunogenicity of PG NSCs. Flow cytometry and immunocytochemistry revealed that both N NSCs and PG NSCs exhibited surface expression of human leukocyte antigen (HLA)-class I but not HLA-DR molecules. Functional analyses using an in vitro mixed lymphocyte reaction assay resulted in less proliferation of peripheral blood mononuclear cells with PG compared to N NSCs. In addition, natural killer cells cytolysed PG less than N NSCs. At a molecular level, expression analyses of immune regulatory factors revealed higher HLA-G levels in PG compared to N NSCs. In line with this finding, MIR152, which represses HLA-G expression, is less transcribed in PG compared to N cells. Blockage of HLA-G receptors ILT2 and KIR2DL4 on NKL cells increased cytolysis of PG NSCs. Together this indicates that PG NSCs have unique immunological properties due to elevated HLA-G expression.