Accumulating data suggest that endocrine disruptors affect not only the reproductive system, but also the immune system. We demonstrate here that endocrine disruptors including diethylstilbestrol (DES) and bisphenol-A (BPA) enhance autoantibody production by B1 cells both in vitro and in vivo. BWF1 mice, a murine model for systemic lupus erythematosus (SLE), implanted with Silastic tubes containing DES after orchidectomy developed murine lupus characterized by immunoglobulin G (IgG) anti-DNA antibody production and IgG deposition in the glomeruli in the kidney as well as those implanted with 17beta-estradiol (E2). Plaque-forming cells (PFC) producing autoantibodies specific for bromelain-treated red blood cells were significantly increased in mice implanted with DES and BPA. IgM antibody production by B1 cells in vitro was also enhanced in the presence of endocrine disruptors including DES and BPA. Estrogen receptor (ER) expression was upregulated in B1 cells in aged BWF1 mice that developed lupus nephritis. These results suggest that endocrine disruptors are involved in autoantibody production by B1 cells and may be an etiologic factor in the development of autoimmune diseases.
B1 cells have different origin and function from conventional B (B2) cells and are considered to be involved in autoantibody production in the development of autoimmune disease. We found that B1 cells preferentially accumulated in the target organs including thymus in aged BWF1 mice, a murine model for systemic lupus erythematosus, and that B lymphocyte chemoattractant (BLC/CXCL13) expression was increased in the thymus before the onset of lupus nephritis, while stromal cell-derived factor-1 (SDF-1/CXCL12) and secondary lymphoid tissue chemokine (SLC/CCL21) expression remained unchanged. Adhesion molecules such as peripheral node addressin (PNAd), ICAM-1, and VCAM-1 were also expressed on endothelial cells in the enlarged thymic perivascular space (PVS) in aged BWF1 mice. BLC protein and PNAd were co-localized on these high-endothelial-venules-like vessels in enlarged PVS. B1 cells expressed higher level of costimulatory molecules and showed a potent antigen-presenting activity in allogeneic mixed lymphocyte reaction comparable to splenic dendritic cells. Interestingly, B1 cells stimulated proliferation of autologous thymic CD4 T cells in the presence of IL-2. These results indicate that aberrant B1 cell trafficking into the thymus due to ectopic high expression of BLC may result in an activation of self-reactive T cells in the development of murine lupus.
We previously reported that B lymphocyte chemoattractant (BLC; CXCL13) was highly and ectopically expressed in aged (NZB × NZW)F1 (BWF1) mice developing lupus nephritis, and that B1 cells were preferentially chemoattracted toward BLC. We demonstrate in this study that B1 cells fail to home to the peritoneal cavity in aged BWF1 mice developing lupus nephritis, and that they are preferentially recruited to the target organs including the kidney, lung, and thymus when injected i.v. In contrast, B1 cells homed to the peritoneal cavity in aged BALB/c mice as effectively as in young mice. Accumulation of B1 cells to the omentum milky spots was also impaired in aged BWF1 mice compared with young mice. CD11bhighF4/80high cells with macrophage morphology were confirmed to be a major cell source for BLC in the peritoneal cavity both in young and aged BWF1 mice. However, the number of BLC-producing peritoneal macrophages was markedly decreased in aged BWF1 mice. These results suggest that the decreased number of BLC-producing peritoneal macrophages together with ectopic high expression of BLC in aged BWF1 mice result in abnormal B1 cell trafficking during the development of murine lupus.
Dendritic cells (DC) play a pivotal role in regulating immune responses. We previously reported aberrant high production of B lymphocyte chemoattractant (BLC/CXCL13) by DC in aged BWF1 mice, amurine model for systemic lupus erythematosus (SLE). We describe here that CD11b+CD11c+ cells were markedly increased in the peripheral blood (PBL‐DC) in aged BWF1, but not in similarly aged NZB or NZW mice. Part of PBL‐DC showed a typical dendritic morphology and expressed MHC class II molecules, and had a weak, but significant antigen‐presenting ability in mixed lymphocytereaction. PBL‐DC were chemoattracted to several chemokines in vitro including secondary lymphoid tissue chemokine (SLC), liver and activation‐regulated chemokine (LARC), RANTES, macrophageinflammatory protein‐1α, whereas splenic mature DC from aged BWF1 mice were preferentially chemoattracted towards SLC. BLC production was induced when PBL‐DC were cultured in the presence of TNF‐α for 3 days. BLC expression was also induced in bone marrow‐derived DC when they were differentiated into mature DC in the presence of TNF‐α and IL‐1β, while both IFN‐α and IFN‐γ failed to induce BLC expression in bone marrow‐derived DC. Since TNF‐α expression is increased in aged BWF1 mice, DC recruitment in the circulation and maturation into BLC‐producing DC by TNF‐α may play a pivotal role in the development of systemic autoimmune diseases.
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