Induction of Tolerogenic Dendritic Cells by a Noncoding Oligonucleotide

Tolerogenic dendritic cells (tolDCs) that dampen T cell responses can be induced from blood monocytes in vitro using factors such as Vitamin D3 (VitD), dexamethasone, IL-10, or rapamycin. However, challenges remain in obtaining robust and efficient generation of cell therapy-based tolDCs without compromising their viability. We recently reported that CCR2-dependent recruitment of monocytic cells, with the capacity to dampen T-helper responses, occurs in mice treated with a single-stranded oligonucleotide (ssON). Here, we investigated the effects of this immunomodulatory noncoding ssON on differentiating human monocytes towards DC in the presence of IL-4 and GM-CSF (moDC). The moDC differentiated in the presence of ssON upregulated CD1a but also increased their expression of PD-L1. The differentiation of monocytes to moDC in the presence of ssON introduced transcriptomic changes, many of which overlapped with VitD-moDC and resulted in moDCs with altered lipopolysaccharide (LPS)-responsiveness. Moreover, ssON-moDC exhibited a low capacity to stimulate alloreactive T cells in vitro and instead promoted the induction of CD4⁺FoxP3⁺CD25⁺ T cells. Experiments using chemical reagents support a role for PPAR-γ in the generation of ssON-moDC. Collectively, our data show that monocytes differentiated with IL-4, GM-CSF, and ssON generate cells with phenotypic and functional characteristics of tolDCs.