Ligation of CD180 contributes to endotoxic shock by regulating the accumulation and immunosuppressive activity of myeloid-derived suppressor cells through STAT3

Myeloid-derived suppressor cells (MDSCs) play an immunosuppressive role in the pathogenesis of inflammatory diseases. CD180, a TLR-like protein, can regulate the proliferation and activation of immune cells. However, the roles of CD180 in regulating the accumulation and function of MDSCs have not been investigated. Here, we found that, compared with non-treated controls, the expression of CD180 was significantly elevated in MDSCs, especially granulocytic MDSCs (G-MDSCs), from mice challenged with lipopolysaccharide (LPS). Ligation of CD180 by the anti-CD180 antibody not only blocked the expansion of MDSCs by preventing the phosphorylation of signal transducer and activator of transcription 3 (STAT3), but also reduced the immunosuppressive activity of MDSCs on M1 macrophage polarization through inhibition of Arg-1 expression in vitro. In vivo studies showed that injection of anti-CD180 antibody significantly aggravated pathological lesions in mice challenged with LPS. Furthermore, injection of anti-CD180 antibody inhibited the accumulation of G-MDSCs in mice challenged with LPS and reduced the immunosuppressive activity of G-MDSCs on M1 macrophage polarization. Based on these findings, we conclude that ligation of CD180 contributes to the pathogenesis of endotoxic shock by inhibiting the accumulation and immunosuppressive activity of G-MDSCs, thus providing insight into the function of CD180 in inflammatory diseases.