Human natural killer cells exhibit negative regulatory function by ectopic expression of hFoxp3 gene

Foxp3 is a key marker of CD4CD25 regulatory T cells and appears highly specific for regulatory T cells. Human dendritic cells transfected with foxp3 gene also exhibit immunosuppressive functions. We want to understand whether natural killer (NK) cells could be endowed with regulatory properties by transduction of Foxp3 gene.

A recombinant vector (pRV.GFP Foxp3) or control vector (pRV.GFP WWRR) was transferred into NKL/NK-92 cells by an electroporation method. The hFoxp3 gene-modified NK cells were characterized with regard to their proliferation, cytokine production, and cytotoxicity and their regulatory effects on activated human peripheral blood mononuclear cells (hPBMCs) in vitro and trans vivo delayed-type hypersensitivity assay.

We found that the ectopic expression of hFoxp3 in human NK cells resulted in the high production of the immunosuppressive cytokine, interleukin (IL)-10. Luciferase reporter assay showed that the expression of IL-10 is directly regulated by Foxp3. We observed that NKL.Foxp3 cells inhibited the proliferation and activation of phorbol-12-myristate-13-acetate/ionomycin-stimulated hPBMCs; furthermore, NKL.Foxp3 cells significantly suppressed the delayed-type hypersensitivity response, which was induced by anti-CD3 monoclonal antibody-activated hPBMCs. NKL.Foxp3 cell-mediated negative regulatory function was dependent on IL-10 production.

Our findings indicated that NK cells acquired IL-10 phenotype by transduction with foxp3 gene and provided evidence that Foxp3 could exert regulatory function not only in regulatory T cells but also in NK cells. These results suggested that Foxp3 gene-modified NK cells might be potential usefulness on graft-versus-host disease or some autoimmune diseases.