St. Vincent's Institute, Fitzroy, Victoria, Australia.
PLoS One. 2012;7(7):e40357. doi: 10.1371/journal.pone.0040357. Epub 2012 Jul 9.
Pancreatic beta cell destruction in type 1 diabetes is mediated by cytotoxic CD8(+) T lymphoctyes (CTL). Granzyme B is an effector molecule used by CTL to kill target cells. We previously showed that granzyme B-deficient allogeneic CTL inefficiently killed pancreatic islets in vitro. We generated granzyme B-deficient non-obese diabetic (NOD) mice to test whether granzyme B is an important effector molecule in spontaneous type 1 diabetes. Granzyme B-deficient islet antigen-specific CD8(+) T cells had impaired homing into islets of young mice. Insulitis was reduced in granzyme B-deficient mice at 70 days of age (insulitis score 0.043±0.019 in granzyme B-deficient versus 0.139±0.034 in wild-type NOD mice p<0.05), but was similar to wild-type at 100 and 150 days of age. We observed a reduced frequency of CD3(+)CD8(+) T cells in the islets and peripheral lymphoid tissues of granzyme B-deficient mice (p<0.005 and p<0.0001 respectively), but there was no difference in cell proportions in the thymus. Antigen-specific CTL developed normally in granzyme B-deficient mice, and were able to kill NOD islet target cells as efficiently as wild-type CTL in vitro. The incidence of spontaneous diabetes in granzyme B-deficient mice was the same as wild-type NOD mice. We observed a delayed onset of diabetes in granzyme B-deficient CD8-dependent NOD8.3 mice (median onset 102.5 days in granzyme B-deficient versus 57.50 days in wild-type NOD8.3 mice), which may be due to the delayed onset of insulitis or inefficient priming at an earlier age in this accelerated model of diabetes. Our data indicate that granzyme B is dispensable for beta cell destruction in type 1 diabetes, but is required for efficient early activation of CTL.
1 型糖尿病中胰腺β细胞的破坏是由细胞毒性 CD8(+)T 淋巴细胞（CTL）介导的。颗粒酶 B 是 CTL 用来杀死靶细胞的效应分子。我们之前曾表明，颗粒酶 B 缺陷的同种异体 CTL 在体外不能有效地杀死胰岛。我们生成了颗粒酶 B 缺陷的非肥胖型糖尿病（NOD）小鼠，以测试颗粒酶 B 是否是自发性 1 型糖尿病的重要效应分子。颗粒酶 B 缺陷的胰岛抗原特异性 CD8(+)T 细胞向年轻小鼠胰岛的归巢能力受损。70 天时，颗粒酶 B 缺陷小鼠的胰岛炎减少（颗粒酶 B 缺陷小鼠的胰岛炎评分 0.043±0.019，而野生型 NOD 小鼠为 0.139±0.034，p<0.05），但在 100 和 150 天时与野生型相似。我们观察到颗粒酶 B 缺陷小鼠胰岛和外周淋巴组织中 CD3(+)CD8(+)T 细胞的频率降低（分别为 p<0.005 和 p<0.0001），但胸腺中的细胞比例没有差异。颗粒酶 B 缺陷小鼠中抗原特异性 CTL 正常发育，并能像野生型 CTL 一样在体外有效地杀死 NOD 胰岛靶细胞。颗粒酶 B 缺陷小鼠自发性糖尿病的发生率与野生型 NOD 小鼠相同。我们观察到颗粒酶 B 缺陷的 CD8 依赖性 NOD8.3 小鼠糖尿病的发病时间延迟（颗粒酶 B 缺陷组的中位发病时间为 102.5 天，野生型 NOD8.3 小鼠为 57.50 天），这可能是由于在这种加速的糖尿病模型中，胰岛炎的发病时间延迟或早期的低效启动。我们的数据表明，颗粒酶 B 对于 1 型糖尿病中β细胞的破坏是可有可无的，但对于 CTL 的早期有效激活是必需的。
