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Abstract：
BACKGROUND: We aimed to investigate whether alpha-galactosylceramide (α-GalCer)-producing Bacteroides fragilis could induce natural killer T (NKT) cells in nonobese diabetic (NOD) mice and reduce their diabetes incidence.
METHODS: Five-week-old female NOD mice were treated orally with B. fragilis, and islet pathology and diabetes onset were monitored. Immune responses were analyzed by flow cytometry and multiplex technology. Effects of ultraviolet (UV)-killed α-GalCer-producing B. fragilis and their culture medium on invariant NKT (iNKT) cells were tested ex vivo on murine splenocytes, and the immunosuppressive capacity of splenocytes from B. fragilis-treated NOD mice were tested by adoptive transfer to nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice.
RESULTS: B. fragilis reduced the diabetes incidence from 69% to 33% and the percent of islets with insulitis from 40% to 7%, which doubled the serum insulin level compared with the vehicle-treated control mice. Furthermore, the early treatment reduced proinflammatory mediators in the serum, whereas the proportion of CD4+ NKT cell population was increased by 33%. B. fragilis growth media stimulated iNKT cells and anti-inflammatory M2 macrophages ex vivo in contrast to UV-killed bacteria, which had no effect, strongly indicating an α-GalCer-mediated effect. Adoptive transfer of splenocytes from B. fragilis-treated NOD mice induced a similar diabetes incidence as splenocytes from untreated NOD mice.
CONCLUSIONS: B. fragilis induced iNKT cells and M2 macrophages and reduced type 1 diabetes in NOD mice. The protective effect seemed to be more centered on gut-pancreas interactions rather than a systemic immunosuppression. B. fragilis should be considered for probiotic use in individuals at risk of developing type 1 diabetes.
METHODS: Five-week-old female NOD mice were treated orally with B. fragilis, and islet pathology and diabetes onset were monitored. Immune responses were analyzed by flow cytometry and multiplex technology. Effects of ultraviolet (UV)-killed α-GalCer-producing B. fragilis and their culture medium on invariant NKT (iNKT) cells were tested ex vivo on murine splenocytes, and the immunosuppressive capacity of splenocytes from B. fragilis-treated NOD mice were tested by adoptive transfer to nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice.
RESULTS: B. fragilis reduced the diabetes incidence from 69% to 33% and the percent of islets with insulitis from 40% to 7%, which doubled the serum insulin level compared with the vehicle-treated control mice. Furthermore, the early treatment reduced proinflammatory mediators in the serum, whereas the proportion of CD4+ NKT cell population was increased by 33%. B. fragilis growth media stimulated iNKT cells and anti-inflammatory M2 macrophages ex vivo in contrast to UV-killed bacteria, which had no effect, strongly indicating an α-GalCer-mediated effect. Adoptive transfer of splenocytes from B. fragilis-treated NOD mice induced a similar diabetes incidence as splenocytes from untreated NOD mice.
CONCLUSIONS: B. fragilis induced iNKT cells and M2 macrophages and reduced type 1 diabetes in NOD mice. The protective effect seemed to be more centered on gut-pancreas interactions rather than a systemic immunosuppression. B. fragilis should be considered for probiotic use in individuals at risk of developing type 1 diabetes.
摘要：
背景：我们旨在研究产生α-半乳糖神经酰胺（α-GalCer）的脆弱拟杆菌是否可以在非肥胖糖尿病（NOD）小鼠中诱导自然杀伤T（NKT）细胞并降低其糖尿病发病率。
方法：用脆弱芽孢杆菌口服治疗五周龄雌性NOD小鼠，监测胰岛病理和糖尿病发病。通过流式细胞术和多重技术分析免疫应答。体外测试了紫外线（UV）杀死的α-GalCer产生的脆弱芽孢杆菌及其培养基对不变NKT（iNKT）细胞的影响，并且通过过继转移至非肥胖糖尿病/严重联合免疫缺陷（NOD/SCID）小鼠来测试来自脆弱芽孢杆菌治疗的NOD小鼠的脾细胞的免疫抑制能力。
结果：B.脆弱性将糖尿病发病率从69%降低到33%，胰岛炎的百分比从40%降低到7%，与载体处理的对照小鼠相比，血清胰岛素水平翻了一番。此外，早期治疗减少了血清中的促炎介质，而CD4+NKT细胞的比例增加了33%。与紫外线杀死的细菌相比，脆弱芽孢杆菌生长培养基刺激的iNKT细胞和抗炎M2巨噬细胞离体，没有效果，强烈表明α-GalCer介导的作用。来自脆弱芽孢杆菌处理的NOD小鼠的脾细胞的过继转移诱导了与来自未处理的NOD小鼠的脾细胞相似的糖尿病发生率。
结论：B.在NOD小鼠中脆弱诱导iNKT细胞和M2巨噬细胞并减少1型糖尿病。保护作用似乎更集中在肠-胰腺相互作用上，而不是系统性免疫抑制。脆弱芽孢杆菌应考虑在有患1型糖尿病风险的个体中使用益生菌。
方法：用脆弱芽孢杆菌口服治疗五周龄雌性NOD小鼠，监测胰岛病理和糖尿病发病。通过流式细胞术和多重技术分析免疫应答。体外测试了紫外线（UV）杀死的α-GalCer产生的脆弱芽孢杆菌及其培养基对不变NKT（iNKT）细胞的影响，并且通过过继转移至非肥胖糖尿病/严重联合免疫缺陷（NOD/SCID）小鼠来测试来自脆弱芽孢杆菌治疗的NOD小鼠的脾细胞的免疫抑制能力。
结果：B.脆弱性将糖尿病发病率从69%降低到33%，胰岛炎的百分比从40%降低到7%，与载体处理的对照小鼠相比，血清胰岛素水平翻了一番。此外，早期治疗减少了血清中的促炎介质，而CD4+NKT细胞的比例增加了33%。与紫外线杀死的细菌相比，脆弱芽孢杆菌生长培养基刺激的iNKT细胞和抗炎M2巨噬细胞离体，没有效果，强烈表明α-GalCer介导的作用。来自脆弱芽孢杆菌处理的NOD小鼠的脾细胞的过继转移诱导了与来自未处理的NOD小鼠的脾细胞相似的糖尿病发生率。
结论：B.在NOD小鼠中脆弱诱导iNKT细胞和M2巨噬细胞并减少1型糖尿病。保护作用似乎更集中在肠-胰腺相互作用上，而不是系统性免疫抑制。脆弱芽孢杆菌应考虑在有患1型糖尿病风险的个体中使用益生菌。
