The overall goal of this revised proposal is to identify the mechanisms by which IL-17 and IFN1 act in concert to initiate the development of B cells that produce autoantibodies in the BXD2 model of autoimmunity. We have found that both IL-17 and IFN1 are required for the formation of germinal centers (GCs) that enable the production of pathogenic autoantibodies in autoimmune BXD2 mice, i.e., a deficiency of either of these cytokines abrogates GC formation, autoantibody formation, and autoimmune disease in these mice. Analysis of the effects of IL-17 on GC formation in the BXD2 mice suggest that IL-17 facilitates the interaction of CD4 T cells and B cells thereby enhancing the formation and stabilization of spontaneous germinal centers (GCs), and that this effect is mediated by upregulation of regulators of G-protein signaling (Rgs)13 and Rgs16 in the B cells. The principal investigator's most recent results indicate that there is an increased number of plasmacytoid DCs (pDCs) in the marginal sinus in BXD2 mice and that these pDCs exhibit significantly elevated expression of IFN1. Notably, there is a robust marginal zone precursor B cell population (MZP) that exhibits an enhanced ability to transport antigen (Ag) directly into a GC light zone area. Based on our accumulated preliminary data, we have formulated a hypothetical model in which IL-17 and IFNa act in a coordinated manner to facilitate the spontaneous GC response through regulating the migration behavior of Ag-transporting MZP B cells. We propose to test this hypothetical model by addressing two of its essential components: (1) Does IFNa regulate influx and IL-17 regulate the retention of MZP in the GC LZ area? (2) Do IFNa and IL-17 regulate Ag transport by MZP B cells leading to GC development? To answer the first question, the ability of IL-17 and IFNa to regulate chemotaxis will be determined in vitro using a transwell chamber, and in vivo by analyzing homing of GFP+ MZP B cells in BXD2 mice in which IL-17R, IFNaR, or Rgs genes has been modulated. This will be achieved by using B cells obtained from BXD2-Il-17r-/-, BXD2-Ifnar-/-, BXD2-Rgs13-/- and BXD2-Rgs16-/- mice. To answer the second question, in vivo Ag capture and transportation by MZP B cells will be determined by FACS and confocal imaging analyses. The Ag transport function of MZP B cells will be studied using the hen egg lysozyme (HEL) or HEL-ovalbumin (OVA) conjugate strategies in combination with BXD2 mice that express the MD4 B-cell receptor transgene and the OVA T-cell receptor transgene.
Successful accomplishment of the project will help to identify critical migratory signals and upstream mediators that facilitate the transportation of Ag to initiate a GC response. The results will provide new insights into the mechanisms of action of currently used therapies based on modulation of IFN1 as well as the proposed targeting of Th17 cells in autoimmune disease as well as suggesting novel targets for therapeutic intervention.
In this project, we propose that local production of immune mediators in the secondary lymphoid organ facilitates specialized B cells that transport antigens into the antibody formation area called germinal centers in autoimmune BXD2 mice. The combination of these events results in the initiation of the chain reaction that leads to the production of pathogenic autoantibodies. An understanding of this process will help to identify a novel therapeutic intervention to prevent the generation of pathogenic autoantibodies as well as suggesting more effective utilization of currently available therapeutic strategies for various autoimmune diseases including lupus and rheumatoid arthritis.
|Hamilton, Jennie A; Li, Jun; Wu, Qi et al. (2015) General Approach for Tetramer-Based Identification of Autoantigen-Reactive B Cells: Characterization of La- and snRNP-Reactive B Cells in Autoimmune BXD2 Mice. J Immunol 194:5022-34|
|Ding, Yanna; Mountz, John D; Hsu, Hui-Chen (2015) Identification of follicular T helper cells in tissue sections. Methods Mol Biol 1291:13-25|
|Li, Hao; Fu, Yang-Xin; Wu, Qi et al. (2015) Interferon-induced mechanosensing defects impede apoptotic cell clearance in lupus. J Clin Invest 125:2877-90|
|Ding, Yanna; Li, Jun; Yang, PingAr et al. (2014) Interleukin-21 promotes germinal center reaction by skewing the follicular regulatory T cell to follicular helper T cell balance in autoimmune BXD2 mice. Arthritis Rheumatol 66:2601-12|
|Li, Hao; Hsu, Hui-Chen; Wu, Qi et al. (2014) IL-23 promotes TCR-mediated negative selection of thymocytes through the upregulation of IL-23 receptor and RORÎ³t. Nat Commun 5:4259|
|Sang, Allison; Zheng, Ying-Yi; Yin, Yiming et al. (2014) Dysregulated cytokine production by dendritic cells modulates B cell responses in the NZM2410 mouse model of lupus. PLoS One 9:e102151|
|Li, Jun; Hsu, Hui-Chen; Ding, Yana et al. (2014) Inhibition of fucosylation reshapes inflammatory macrophages and suppresses type II collagen-induced arthritis. Arthritis Rheumatol 66:2368-79|
|Li, Hao; Wu, Qi; Li, Jun et al. (2013) Cutting Edge: defective follicular exclusion of apoptotic antigens due to marginal zone macrophage defects in autoimmune BXD2 mice. J Immunol 190:4465-9|
|Li, Jun; Yang, PingAr; Wu, Qi et al. (2013) Death receptor 5-targeted depletion of interleukin-23-producing macrophages, Th17, and Th1/17 associated with defective tyrosine phosphatase in mice and patients with rheumatoid arthritis. Arthritis Rheum 65:2594-605|
|Wang, John H; New, James S; Xie, Shutao et al. (2013) Extension of the germinal center stage of B cell development promotes autoantibodies in BXD2 mice. Arthritis Rheum 65:2703-12|
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