McKenzie Mark D, Dudek Nadine L, Mariana Lina, Chong Mark Mw, Trapani Joseph A, Kay Thomas Wh, Thomas Helen E
St Vincent's Institute, Fitzroy, Melbourne, Australia.
Int Immunol. 2006 Jun;18(6):837-46. doi: 10.1093/intimm/dxl020. Epub 2006 Mar 30.
Direct interaction between auto-reactive CTL and specific peptide-MHC class I complexes on pancreatic beta cells is critical in mediating beta cell destruction in type I diabetes. We used mice with genetic modifications in three major pathways used by CTL, perforin, Fas and pro-inflammatory cytokines to assess the relative contribution of these mechanisms to beta cell death. In vitro-activated ovalbumin (OVA)-specific CTL, from OT-I TCR-transgenic mice, specifically killed transgenic beta cells expressing OVA (from RIP-mOVA mice) in a 16-h cytotoxicity assay. Perforin-deficient CTL had a reduced ability to kill OVA-expressing islets in vitro (22.1 +/- 3.8%) compared with wild-type CTL (71.4 +/- 4.6%). Fas-deficient islets were only slightly protected from wild-type CTL but were completely protected from the residual killing observed with perforin-deficient CTL. Residual cytotoxicity in perforin-deficient CTL was also prevented by overexpression of SOCS-1, which blocks multiple cytokine signaling pathways. It was also prevented by pre-incubation with anti-tumor necrosis factor-alpha (anti-TNFalpha) antibody or by blocking IFNgamma responsiveness through expressing a dominant negative IFNgamma receptor. Perforin-deficient CTL produced IFNgamma and TNFalpha that was shown to directly induce islet Fas expression during the assays. This suggests that Fas-deficiency, SOCS-1 overexpression and blockade of IFNgamma and TNFalpha all protect beta cells from residual cytotoxicity of perforin-deficient CTL by blocking Fas upregulation. These findings indicate that wild-type CTL destroy antigen-expressing islets via a perforin-dependent mechanism. However, in the absence of perforin, the Fas/FasL pathway provides an alternative mechanism dependent on islet cell Fas upregulation by cytokines IFNgamma and TNFalpha.
自身反应性细胞毒性T淋巴细胞（CTL）与胰腺β细胞上特定的肽 - 主要组织相容性复合体I类复合物之间的直接相互作用在介导I型糖尿病中β细胞破坏方面至关重要。我们使用在CTL、穿孔素、Fas和促炎细胞因子所使用的三个主要途径中进行了基因改造的小鼠，来评估这些机制对β细胞死亡的相对贡献。在体外激活的来自OT - I TCR转基因小鼠的卵清蛋白（OVA）特异性CTL，在16小时的细胞毒性试验中特异性杀死了表达OVA的转基因β细胞（来自RIP - mOVA小鼠）。与野生型CTL（71.4±4.6%）相比，穿孔素缺陷型CTL在体外杀死表达OVA的胰岛的能力降低（22.1±3.8%）。Fas缺陷型胰岛仅受到轻微保护以免受野生型CTL的攻击，但完全受到保护以免受穿孔素缺陷型CTL所观察到的残余杀伤作用。通过过表达SOCS - 1（其阻断多种细胞因子信号通路）也可防止穿孔素缺陷型CTL中的残余细胞毒性。通过用抗肿瘤坏死因子 - α（抗TNFα）抗体预孵育或通过表达显性负性IFNγ受体来阻断IFNγ反应性也可防止这种情况。穿孔素缺陷型CTL产生IFNγ和TNFα，在试验过程中这些因子被证明可直接诱导胰岛Fas表达。这表明Fas缺陷、SOCS - 1过表达以及IFNγ和TNFα的阻断都通过阻断Fas上调来保护β细胞免受穿孔素缺陷型CTL的残余细胞毒性作用。这些发现表明野生型CTL通过穿孔素依赖性机制破坏表达抗原的胰岛。然而，在没有穿孔素的情况下，Fas/FasL途径提供了一种依赖于细胞因子IFNγ和TNFα上调胰岛细胞Fas的替代机制。
