Dendritic cell subsets in autoimmune diabetes

DEC-205是由不同的CD 8 α +树突细胞亚群表达的内吞受体。 通过嵌合抗体构建体将蛋白质靶向DEC-205导致免疫正常小鼠中抗原特异性CD 4+和CD 8 + T细胞的克隆缺失或无反应性。 在NOD小鼠（一种自身免疫性糖尿病的小鼠模型）中，β细胞特异性CD 8 + T细胞可通过抗DEC抗原治疗而耗尽（Mukhopadhaya A等人，PNAS 2008）。 我们现在正在评估DEC-205靶向自身免疫NOD小鼠中耗尽或无反应性CD 4 + T细胞的能力。 向NOD小鼠注射识别未知β细胞抗原的BDC2.5 T细胞受体（TCR）转基因CD 4 + T细胞，然后用连接至BDC模拟位肽的抗DEC-205处理。在抗DEC-205处理后三天，BDC T细胞在淋巴器官中增殖，与正常小鼠中的结果相似。然而，在用抗DEC-205治疗后10天，当正常小鼠中的T细胞被删除时，抗原特异性细胞保留在自身免疫小鼠中并且不是无反应性的（它们保留了产生干扰素γ的能力）。 我们现在正在评估在这种情况下，哪些免疫途径可能对诱导耐受性很重要。 CD 11b+树突状细胞在其表面上表达DCIR 2，并且DCIR 2特异性抗体可用于将抗原靶向该DC亚群。 我们现在测量在NOD小鼠中用抗DCIR 2靶向BDC肽体内刺激后的BDC2.5 TCR转基因T细胞应答。 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。 另一种类型的DC，浆细胞样DC（pDC），由于其在刺激时分泌大量1型IFN的能力，传统上已被鉴定为DC的独特子集，其作为先天免疫细胞参与病毒免疫。然而，最近，pDC也显示出向CD 4 T细胞呈递抗原，并且在诱导免疫耐受中至关重要。我们现在通过1）研究NOD小鼠和非自身免疫品系中糖尿病进展不同阶段的pDC数量来解决pDC在自身免疫性糖尿病发病机制中的作用。2)了解糖尿病易感基因如何影响pDC发育，重点关注易感基因Idd 3和Idd 5。 在未来，我们将耗尽NOD小鼠中的pDC，并确定这是否会影响糖尿病的发展。 我们还评估了IL-2（小鼠和人类的自身免疫性糖尿病易感基因）如何影响DC发育。 使用FMS样酪氨酸激酶3配体（Flt 3L）刺激的骨髓细胞培养物，我们已经表明IL-2抑制cDC和pDC发育。 此外，在IL-2存在下发育的DC显示刺激T细胞增殖的能力降低。 IL-2可能在MDP阶段起作用，因为它们是表达IL-2 Ra的前体，并且MDP在具有Flt 3L和IL-2的培养物中积累。

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). We are now assessing the ability of DEC-205 targeting to deplete or anergize CD4+ T cells in autoimmune NOD mice. NOD mice were injected with BDC2.5 T cell receptor (TCR) transgenic CD4+ T cells that recognize an unknown beta cell antigen, 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). We are now assessing what immune pathways may be important for inducing tolerance in this setting. 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. Another type of DC, Plasmacytoid DCs (pDC) have traditionally been identified as a distinct subset of DCs involved as an innate immune cell in viral immunity due to their ability to secrete large amount of type 1 IFN upon stimulation. However, more recently, pDCs have also been shown to present antigen to CD4 T cells and to be vital in the induction of immune tolerance. We are now addressing the role of pDC in the pathogenesis of autoimmune diabetes by 1) studying the number of pDCs at different stages of diabetes progression in the NOD mice, and in non autoimmune strains. 2) understanding how diabetes susceptibility genes affect pDC development, focusing on genes found in the susceptibility loci Idd3 and Idd5. In the future, we will deplete pDCs in NOD mice and determine if this affects diabetes development. We have also assessed how IL-2, an autoimmune diabetes susceptibility gene in both mouse and human, affects DC development. Using cultures of bone marrow cells stimulated with FMS-like tyrosine kinase 3 ligand (Flt3L), we have shown that IL-2 inhibits both cDC and pDC development. Furthermore, DCs that do develop in the presence of IL-2 display reduced ability to stimulate T cell proliferation. IL-2 is likely acting at the MDP stage because those are the precursors that express the IL-2Ra, and MDPs accumulate in cultures with Flt3L and IL-2.