Regulatory B Cells in the Amelioration of Immune-mediated Periodontal Disease

This application is for the competitive renewal of our current R01 grant titled “Regulatory B cells in the amelioration of immune-mediated periodontal disease”, which has produced a total of 23 related publications so far. Our studies have focused on the anti-inflammatory role of B10 cells in periodontal disease tissue destruction and bone resorption. Specifically, we demonstrated that B10 cells can be activated and expanded following triggering by specific TLR signaling and co-stimulatory molecules and thereby inhibit local inflammation and bone loss in experimental periodontitis in vivo. The observed anti-inflammatory effects are associated with IL-10 secretion by B10 cells. While substantiating the anti-inflammatory actions of these cells, the potential role of B10 cells in the resolution of inflammation is largely unknown. Our recent data using multiphoton intravital microscopy demonstrated co-localization of monocytes/ macrophages with transferred B10 cells in gingival tissue of LPSinduced gingivitis. In vitro, the expression level of PD-L1 was elevated in activated B10 cells from mouse splenocytes or human peripheral blood mononuclear cells (PBMC). Co-culture of activated B10 cells with monocytic cell line (THP-1)-derived macrophages up-regulated PD-1 expression onmacrophages and increased the production of specialized pro-resolving mediators (SPM) by macrophages. These effects were diminished when direct contact between B10 and macrophages was blocked. Together with the previously published findings by others, we hypothesize that i) activated B10 cells induce pro-resolving macrophage differentiation and specialized pro-resolving mediators (SPM) production via PD-L1/PD-1 ligation, and that ii) actions of SPM derived from B10-macrophage interaction enhance both B10 cell differentiation to antibody-secreting cells and pro-resolving macrophage function to promote inflammation resolution. In this proposal, we will first determine the role of PD-L1/PD-1 ligation on B10-mediated regulation of macrophage phenotype switch and production of lipid mediators using B10-macrophage co-cultures and animal model of experimental periodontitis with adoptive B10 cell transfer (Aim 1); Then the actions of SPM on B10 differentiation during B10-macrophage interaction will be determined, together with their effects on B cell mediated pathogen clearance, and inhibition of gingival inflammation and periodontal bone loss (Aim 2); Thirdly, B10-macrophage interaction on pro-resolving macrophages function, neutrophil activity, and the subsequent resolution of periodontal inflammation will be determined (Aim 3). Successful completion of this project will generate conceptual advances in our understanding of the immune regulatory cell-cell interactions and their impact on the resolution of inflammation. If our hypothesis is correct, these studies will broaden our insights into the potential role of immune checkpoint molecules PD-L1/PD-1 in the resolution of inflammation in periodontal disease, as well as other immune-mediated osteolytic conditions such as osteoporosis or rheumatoid arthritis