FUNCTIONS OF SHIGA LIKE TOXIN RECEPTORS IN IMMUNE RESPONSES

由大肠杆菌产生的志贺样毒素（SLT，也称为维罗毒素或 VT）。 大肠杆菌血清型 0157;H7 和其他血清型被认为是 出血性结肠炎、血栓性血小板减少症的病原体 紫癜和溶血性尿毒症综合征。 SLT 的受体是 三糖基神经酰胺或 Gb3 (CD77) 以及可能的其他鞘糖脂 其中含有Galalpha1-4Gal残基。 Gb3 的表达方式多种多样 人类细胞类型，包括生发中心 B 淋巴细胞。 Gb3- 结合 SLT B 亚基已被证明可以模仿 63 kD 的亚基 人α-干扰素受体 (IFNAR) 和泛 B 细胞标记物 CD19 它们的氨基酸序列。 迄今为止的实验证据支持这一作用 某些细胞类型中 α-IFN 信号转导中的 Gb3/IFNAR 相互作用 CD19/Gb3 相互作用作为 B 同型粘附和归巢的机制 淋巴细胞。 大多数表达 Gb3 的人类细胞，包括 B 淋巴细胞能够发挥抗原呈递细胞的作用。 因此，SLT可能是抑制肠出血性大肠杆菌的一种手段。 抗体反应和免疫系统的其他功能 感染。 拟议研究的长期目标是确定 Gb3 和其他含 Galalpha1-4Gal 的糖脂的细胞功能 及其内源性蛋白质配体，并确定如何靶向 Gb3和其他含Galalpha1-4Gal的糖脂及其内源性 蛋白质配体并确定 SLT 如何靶向 Gb3 细胞 影响产 SLT 大肠杆菌的免疫反应和发病机制 感染。 具体目标是； 1. 定义涉及人 B 细胞中 Gb3 表达的细胞功能 系和潜在的抗原呈递细胞。 SLT 将用作探针 进一步定义 Gb3 在 B 细胞系上的表达并探讨 细胞因子、表面标记抗体、有丝分裂原和其他诱导剂 Gb3 表达和 SLT 诱导的分化或激活 B 细胞和其他潜在抗原呈递细胞的细胞毒性。 任意 这些药物对野生型 Gb3 细胞与突变型 Gb3 细胞的不同影响 人 B 细胞系中被选择为 Gb3 和 Gb3 结合蛋白的细胞。 CD19（例如 Daudi）和 CD19-（例如 U266）的人类 B 细胞系将被 注射到 SCID 小鼠中以研究 CD19/Gb3 的可能作用 归巢到高 Gb3 表达位点的相互作用。 3. 检查开发细胞毒性小鼠模型的潜力 SLT 和 Gb3 细胞功能对细胞的影响 免疫系统。 Gb3 表达和对 SLT 诱导的敏感性 B不同阶段对应的小鼠细胞系的细胞毒性 细胞发育以及其他具有抗原能力的鼠细胞 演示文稿将与相应人类的 Gb3 成分进行比较 细胞。 给予小鼠不同抗原引起的反应 与 SLT B 亚基的结合将决定 B 亚基是否与 Gb3 细胞具有免疫抑制作用。

Shiga-like toxins (SLT's, also called verotoxins or VT's) produced by E. coli sertotype 0157;H7 and other serotypes have been implicated as causative agents of hemorrhagic colitis, thrombotic thrombocytopenic purpura and hemolytic uremic syndrome. The receptors for the SLT's are globotriaosyl ceramide or Gb3 (CD77) and possibly other glycosphingolipids which cotnain Galalpha1-4Gal residues. Gb3 is expressed on a wide variety of human cell types including germinal center B lymphocytes. The Gb3- binding SLT B subunits have been shown to mimic the 63 kD subunit of the human alpha-interferon receptor (IFNAR) and the pan B cell marker CD19 in their amino acid sequences. Experimental evidence to date supports a role for Gb3/IFNAR interaction in alpha-IFN signaling in some cell types and CD19/Gb3 interaction as a mechanism for homotypic adhesion and homing of B lymphocytes. The majority of human cells which express Gb3, including B lymphocytes, are capable of functioning as antigen-presenting cells. Therefore, SLT's may be a means by which enterohemorrhagic E. coli suppress antibody responses and other functions of the immune system during infection. The long term objectives of the proposed research are to determine the cellular functions of Gb3 and other Galalpha1-4Gal-containing glycolipids and their endogenous protein ligands and to determine how the targeting of Gb3 and other Galalpha1-4Gal-containing glycolipids and their endogenous protein ligands and to determine how the targeting of Gb3+ cells by SLT affects immune responses and athe pathogenesis of SLT-producing E. coli infection. Specific aims are to; 1. Define cell functions which involve Gb3 expression in human B cell lines and potential antigen-presenting cells. SLT's will be used as probes to further define Gb3 expression on B cell lines and to probe the effect of cytokines, antibodies to surface markers, mitogens and other inducers of differentiation or activation on Gb3 expression and SLT-induced cytotoxicity in B cells and other potential antigen presenting cells. Any differential effects of these agents on wild-type Gb3+ cells versus mutant cells selected to be Gb3 and Gb3-binding proteins in human B cell lines. Human B cell lines which are CD19+(e.g. Daudi) and CD19-(e.g. U266) will be injected into SCID mice to investigate a possible role for CD19/Gb3 interaction in homing to sites of high Gb3 expression. 3. Examine the potential of developing a mouse model for the cytotoxic effects of SLT and cellular functions of Gb3 with regard to cells of the immune system. The Gb3 expression and susceptibility to SLT-induced cytotoxicity of murine cell lines corresponding to different stages of B cell development as well as other murine cells capable of antigen presentation will be compared to the Gb3 composition of corresponding human cells. The responses elicited in mice by various antigens administered with SLT B subunits will determine whether the binding of B subunits to Gb3+ cells is immunosuppressive.