Targeting antigen to dendritic cells in autoimmune diabetes

DEC-205是一种内源性受体，由CD8α+树突状细胞亚群表达。在免疫正常的小鼠中，通过嵌合抗体构建物将蛋白质靶向DEC-205会导致抗原特异性的CD4+和CD8+T细胞的克隆性缺失或无能。在NOD小鼠中，一种自身免疫性糖尿病的小鼠模型，β细胞特异性CD8+T细胞可以通过抗DEC抗原治疗而耗尽(MukHopadhaya A等人)。PNAS 2008)。利用DEC-205靶向，我们现在已经确定在自身免疫性NOD小鼠中，CD8树突状细胞不能诱导CD4+T细胞耐受。 NOD小鼠注射BDC2.5 T细胞受体(TCR)转基因的CD4+T细胞，识别β细胞抗原Chromoranin A，然后用BDC模拟表位多肽结合的抗DEC-205进行治疗。在抗DEC-205治疗三天后，BDC T细胞在淋巴器官中增殖，与正常小鼠的结果相似。然而，在用抗DEC-205治疗10天后，当正常小鼠中的T细胞被删除时，自身免疫小鼠中的抗原特异性细胞仍然存在，并且不是无能的(它们保留了产生干扰素伽马的能力)。此外，没有观察到调节性T细胞的增加。因此，针对NOD CD8树突状细胞的抗原不会导致缺失、无能或调节性T细胞(外周T细胞耐受的三种主要机制)。我们感兴趣的是，在这种情况下，哪些免疫途径对于恢复耐受性可能是重要的。CD40/CD40L的相互作用可能是一个重要的途径：当抗CD40L的特异性封闭抗体与抗DEC-205抗原一起给予时，T细胞反应更具耐受性。 CD11b+树突状细胞表面表达DCIR2，针对DCIR2的抗体可用于靶向该DC亚群。我们现在正在检测抗DCIR2靶向BDC多肽在NOD小鼠体内刺激BDC2.5 TCR转基因T细胞后的反应。我们还在测试这种抗体-抗原组合是否可以改变糖尿病的发展。

DEC-205 is an endocytic receptor expressed by a distinct CD8 alpha+ dendritic cell subpopulation. Targeting of proteins to DEC-205 through chimeric antibody constructs causes clonal deletion or anergy of antigen-specific CD4+ and CD8+ T cells in immunologically normal mice. In NOD mice, a mouse model for autoimmune diabetes, beta cell-specific CD8+ T cells can be depleted by anti-DEC antigen treatment (Mukhopadhaya A, et al. PNAS 2008). Using DEC-205 targeting, we have now determined that in autoimmune NOD mice, CD8 DCs are not able to induce CD4+ T cell tolerance. NOD mice were injected with BDC2.5 T cell receptor (TCR) transgenic CD4+ T cells that recognize the beta cell antigen chromogranin A, followed by treatment with anti-DEC-205 attached to a BDC mimeotope peptide. Three days after anti-DEC-205 treatment, BDC T cells had proliferated in lymphoid organs, similar to results in normal mice. However, ten days after treatment with anti-DEC-205, when T cells are deleted in normal mice, antigen-specific cells remained in the autoimmune mice and were not anergic (they retained capacity to produce interferon gamma). In addition, no increase in regulatory T cells was observed. Therefore, antigen targeted to NOD CD8 DCs does not induce deletion, anergy or regulatory T cells (the 3 main mechanisms of peripheral T cell tolerance). We are interested in what immune pathways may be important for restoring tolerance in this setting. CD40/CD40L interactions are one pathway that may be important: when a blocking antibody specific for anti-CD40L was given with anti-DEC-205 antigen, T cell responses were more tolerogenic. CD11b+ dendritic cells express DCIR2 on their surface, and antibodies specific for DCIR2 can be used to target antigens to this DC subset. We are now measuring BDC2.5 TCR transgenic T cell responses after stimulation in vivo with anti-DCIR2-targeted BDC peptide in NOD mice. We are also testing whether this antibody-antigen combination can alter diabetes development.