MyD88-silenced dendritic cells induce T-cell hyporesponsiveness and promote Th2 polarization in vivo

Previous studies have determined that the absence of MyD88 enhances the tolerogenicity of dendritic cells (DCs), suggesting that inhibiting innate immunity may be a potential strategy to facilitate the induction of transplant tolerance by DCs. However, the underlying mechanism remains unclear.

Recipient rats were preconditioned with MyD88 gene-silenced DCs. In vivo distribution of infused MyD88 gene-silenced DCs in lymphatic organs was also analyzed. The response ability of recipient spleen T cells was determined by cell proliferation assay. The concentrations of interferon (IFN)-γ, interleukin (IL)-2, IL-4, IL-5 and IL-10 in cell culture supernates were measured with sandwich enzyme-linked immunosorbent assay. Flow cytometry was used to detect the transfection efficiency and CD4(+)CD25(+)FoxP3(+) T cell assay.

After being infused into allogenic recipient rats, both MyD88-or control-silenced DCs were efficiently trafficked to the lymphatic organs and liver. The ex vivo analysis of proliferative responses revealed the donor-specific inhibition of alloimmune reactivity by MyD88-silenced DCs. This effect was associated with the marked inhibition of Th1-type cytokine production (IFN-γ and IL-2) but with significant promotion of Th2 type cytokine secretion (IL-4 and IL-5).

It was demonstrated that T cells from recipients pretreated with MyD88-silenced DCs exhibited significantly reduced secretion of IFN-γ and IL-2 but markedly enhanced production of IL-4 and IL-5.