Abstract:
Tolerogenic dendritic cells (tolDCs) are DCs with an immunoregulatory function, which can induce regulatory T cells (Tregs) and suppress the immune response. Currently, tolDCs-based treatment has become a promising therapeutic approach for organ transplantation and autoimmune disease. FcgRIIB is an inhibitory receptor widely expressed in B cells, myeloid cells, and DCs. The ablation of FcgRIIB in the murine model shows a spontaneous development of a lupus-like disease and might affect other immune cell regulation. There was limited information on tolDC induction in FcgRIIB defective mice. Thus, in this study, we studied the generation of tolDCs from the bone marrow-derived dendritic cells (BMDCs) of Fcgr2b-/- mice by various tolerogenic agents. As expected, when compared with wide-type (WT) control, bone marrow-derived DCs of Fcgr2b-/- mice showed higher activation and pro-inflammatory cytokine productionupon LPS stimulation when compared with wide-type (WT) control. Tolerogenic agents can partially reduce the activation and cytokine production of LPS-stimulated Fcgr2b-/- BMDCs. Mainly, dexamethasone-treated Fcgr2b-/- BMDCs exhibited a notable decrease in pro-inflammatory cytokine production and showed an increase in IL-10 production in response to LPS stimulation. Furthermore, we demonstrated that dexamethasone-conditioned Fcgr2b-/- tolDCs could mediate Treg expansion ex vivo.
For the in vivo treatment of lupus disease, dexamethasone-conditioned Fcgr2b-/- tolDCs were adoptively transferred to Fcgr2b-/- lupus-prone mice, mediated Foxp3+ Treg expansion in the spleens and suppressed anti-double strand DNA autoantibodies in the serum. In addition, to generate tolDCs in vivo more conveniently, dexamethasone-loaded nanoparticles (DexaNPs) designed to target DCs were subcutaneously injected into Fcgr2b-/- lupus-prone mice. The DexaNPs-treated mice showed a significantly enhanced expression of PD-L1 on CD11c+ DCs, increased FoxP3+ Treg numbers, and decreased serum anti-double strand DNA autoantibodies.
In conclusion, our study demonstrated that dexamethasone is the most potent drug that can induce tolerogenic DCs and lead to better clinical outcome in Fcgr2b-/- lupus-prone mice. This may be helpful for DC-based treatment in SLE patients but not limited to FcgrIIb gene polymorphism.
