NKG2D indirectly regulates activation of DCs by interaction with CD4+ T cells
The regulation of NKG2D on DCs was investigated by co-culturing DCs from JIA patients and healthy controls with irradiated CD4+T cells with the genetic modifications of NKG2D. The cytokines secreted by DCs are shown in Figure 5A. In healthy controls, NKG2D significantly decreased the secretion of IL-10 and TGF-β by DCs via the interaction with CD4+ T cells (P<0.05). No significant effect on the production of IL-12 was evident (P>0.05). Additionally, NKG2D decreased the secretion of IL-10 by DCs of JIA patients via the interaction with CD4+T cells (P<0.05). Production of TGF-β and IL-12 was not influenced (P>0.05).
The expressions of the costimulatory molecules CD80 and CD86, and DC maturation markers CD83 and the MHC II receptor HLA-DR were analyzed (Figure 5B). CD83 expression on DCs of JIA patients and healthy controls rose significantly upon interaction with NKG2D overexpressing CD4+ T cells (P<0.05) and vice versa. This expression was significantly lowered by interaction with NKG2D silenced CD4+ T cells (P<0.05). NKG2D genetic modifications had no statistical influences on cellular markers of CD80, CD86 and HLA-DR in the JIA or healthy control groups (P>0.05).
The expressions of the NKG2D ligands MICA and MICB on DCs were tested by flow cytometry (Figure 5C and 5D). NKG2D indirectly upregulated the expression of MICA and MICB on DCs in JIA patients and healthy controls by LV-NKG2D modification in CD4+ T cells (P<0.05). NKG2D also significantly decreased MICA and MICB expressions by LV-siRNA modified CD4+ T cells (P<0.05).