FUNCTIONS OF SHIGA LIKE TOXIN RECEPTORS IN IMMUNE RESPONSES

志贺类毒素(SLT‘s，又称verotoxins或VT’s)是由E. 大肠杆菌血清型0157；H7和其他血清型被认为与 出血性结肠炎、血栓性血小板减少性疾病的病因 紫癜性溶血性尿毒症综合征。SLT的受体是 球三糖神经酰胺或Gb3(CD77)以及可能的其他神经鞘糖脂 其中含有Galalpha1-4Gal残基。Gb3在各种各样的细胞中都有表达 包括生发中心B淋巴细胞在内的人类细胞类型。Gb3- 结合SLT B亚基已被证明模拟63kD亚基的 人α-干扰素受体(IFNAR)和PAN B细胞标志物CD19在 它们的氨基酸序列。到目前为止的实验证据支持一个角色 Gb3/IFNAR在某些细胞类型的α-干扰素信号中的相互作用 CD19/Gb3相互作用作为B细胞同型黏附和归巢的机制 淋巴细胞。大多数表达Gb3的人类细胞，包括B细胞 淋巴细胞具有抗原提呈细胞的功能。 因此，SLT可能是肠出血性大肠杆菌抑制的一种手段。 免疫系统的抗体反应和其他功能 感染。 拟议研究的长期目标是确定 Gb3等含Galalpha1-4Gal糖脂的细胞功能 和他们的内源性蛋白配体，并确定如何靶向 Gb3等含半乳糖1-4半乳糖的糖脂及其内源性 蛋白质配体和确定SLT如何靶向Gb3细胞 影响免疫应答及产SLT大肠杆菌的发病机制 感染。 具体目标是； 1.确定人类B细胞中涉及Gb3表达的细胞功能 品系和潜在的抗原提呈细胞。SLT将用作探测器 进一步明确Gb3在B细胞系中的表达，并探讨Gb3在B细胞中的作用 细胞因子、表面标志抗体、有丝分裂原和其他诱导剂 分化或激活对Gb3表达的影响及SLT诱导 对B细胞和其他潜在的抗原提呈细胞的细胞毒性。任何 这些药物对野生型与突变型Gb3细胞的不同作用 人B细胞系中Gb3和Gb3结合蛋白的筛选细胞。 CD19(如Daudi)和CD19-(如U266)的人B细胞株将是 注射入SCID小鼠研究CD19/Gb3的可能作用 归巢到Gb3高表达位点的相互作用。 3.研究建立细胞毒小鼠模型的可能性 SLT和Gb3对小鼠肾小管上皮细胞的影响 免疫系统。Gb3的表达与SLT诱导的易感性 B细胞不同阶段对应的小鼠细胞系的细胞毒性 细胞发育以及其他能够抗原性的小鼠细胞 演示文稿将与相应人类的Gb3组成进行比较 细胞。不同抗原注射对小鼠的免疫应答 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.