OVA administration had no effect on the CD80, CD86 and I-Ab expression of spleen CD11c+ DCs and the Ulixertinib datasheet number of total CD4+ T cells, with or without IC administration (data not shown). After 5 and 7 days of LPS or CpG ODN administration, IC pretreatment suppressed the increases in total CD4+ T cells in spleen and lymph nodes (Fig. 3A), serum IFN-γ levels (Fig. 3B) and OVA323–339-specific CD4+KJ1.26+ T cells in spleen and lymph nodes (Fig. 3C). To further investigate whether IC-mediated suppression of in vivo T cells response was mediated by FcγRIIb, we performed the experiments described above in FcγRIIb−/− mice. In contrast to WT mice, pretreatment

of FcγRIIb−/− mice with IC did not suppress but instead, increased in vivo T-cell responses in FcγRIIb−/− mice, which was characterized by a significant increase in antigen-specific T cells and serum IFN-γ levels (Fig. 3D and E). Taken together, these data further demonstrate that IC pretreatment could downregulate T-cell responses in vivo to TLR ligands via FcγRIIb. Since IC used in the experiments above was prepared from OVA and anti-OVA mAb, which are not natural IC present in vivo, we isolated natural IC/Ig from MRL/lpr lupus-prone mice and then investigated whether natural IC/Ig also had such inhibitory effects. As Selleckchem Sirolimus expected, IC/Ig derived from MRL/WT and MRL/lpr lupus

mice significantly inhibited LPS or CpG ODN-induced upregulation of I-Ab, CD40, CD80 and CD86 expression on DCs (Fig. 4A), and also inhibited secretion of TNF-α (Fig. 4B). The data show that natural IC/Ig, prepared from mice with PRKACG autoimmune disease, also enhances the resistance of immature DCs to TLR-triggered maturation. Both in vitro and in vivo data above suggest that IC maintains the tolerogenecity of immature DCs in FcγRIIb-dependent manner. Considering that coexpression of activating and inhibitory FcRs

on the same cell will set a threshold for immune cell activation by IC, we tried to overexpress FcγRIIb in immature DCs so as to polarize immature DCs to be dominantly triggered by inhibitory signal once stimulated with IC. Recombinant adenovirus carrying FcγRIIb was constructed and used to transfect immature DCs, and the tolerogenetic properties of DC-FcγRIIb by natural IC/Ig were investigated. Immature DCs transfected with Ad-FcγRIIb at a MOI of 50 or 200 (DC-FcγRIIb) expressed higher levels of FcγRIIb than Ad-LacZ-transfected DCs (DC-LacZ) (Supporting Information Fig. 3). So, an MOI of 50 was used in the following experiments. Natural IC/Ig significantly inhibited DC-FcγRIIb, but not DCs or DC-LacZ, to express I-Ab, CD40, CD80 and CD86 and to secrete TNF-α (Fig. 5A). LPS significantly promoted the three types of DCs to express I-Ab, CD40, CD80 and CD86 and to secrete TNF-α (Fig. 5A and B).