CONTROL OF PERSISTENT ANTIBODY RESPONSE BY FC RECEPTORS

FC 受体控制持续抗体反应

基本信息

批准号：
6511206
负责人：
TIMOTHY L MANSER
金额：
$ 27.45万
依托单位：
THOMAS JEFFERSON UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
1999
资助国家：
美国
起止时间：
1999-05-15 至 2004-04-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/6511206
关键词：
B cell receptor B lymphocyte antibody formation antibody receptor biological signal transduction dendritic cells enzyme linked immunosorbent assay flow cytometry immune complex immunologic memory laboratory mouse leukocyte activation /transformation tissue /cell culture

项目摘要

Long-term persistence of antigen-specific antibody and the generation of highly specific memory B cells are well recognized features of the humoral immune response. The specialized microenvironment of the germinal center (GC) may be key to these pathways, in particular, the ability of the follicular dendritic cells (FDC) to retain immunogenic antigen in the form of immune complexes (ICs) for extended periods. It has been proposed that this form of antigen both drives the selection of high affinity B cell receptor somatic mutants during the primary immune response, and maintains the stability of the memory B cell compartment over extended periods thereafter. Mice deficient in the activation Fc receptors FcgammaRI and FcgammaRIII display dramatically enhanced IC deposition and retention on FDCs. However, this does not lead to perturbation of the primary immune response. In Aim 1, we propose to test the hypothesis that this enhanced IC deposition and retention on FDCs will result in elevated levels of persistent serum antibody, memory B cells, and antibody forming cells (AFCs) in the bone marrow. We will also determine whether retention of ICs on FDCs is stable to subsequent immunization with a second antigen, and whether the affinity of persistent serum antibody is lower when cognate antigen levels on FDC are higher. B cell activity during the generation and maintenance of memory may also be regulated by direct interaction of ICs with antigen specific B cells via the inhibitory FcR, FcgammaRIIB. Mice deficient in this FcR display elevated serum antibody and AFC levels after immunization, consistent with this idea and with past in vitro studies on the functioning of this FcR. However, since FcgammaRIIB is the most widely expressed FcR, found on many myeloid lineages and FDCs, this conclusion remains tentative. In Aim 2 we propose to test the hypothesis that the dysregulated expression of antibody production observed in FcgammaRIIB. deficient mice is due to absence of this FcR on B cells. Finally, recent data have shown that the mechanism of inhibition of BCR signaling upon BCR-FcgammaRIIB co-ligation is mediated by recruitment of the inositol polyphosphate phosphatase SHIP to the ITIM motif in the cytoplasmic tail of FcgammaRIIB. A mutant form of FcgammaRIIB with a Y-greater than F change in the ITIM motif, precluding the Y phosphorylation necessary for SHIP binding, does not mediate inhibition of BCR signaling in transfected cell lines. In Aim 3, we propose to test the hypothesis that the ITIM-SHIP pathway is the only FcgammaRIIB initiated pathway necessary for inhibition of B cell activity in vivo, using mice engineered to express the FcgammaRIIB Y-greater than F mutant in the B cell compartment.

抗原特异性抗体的长期持续存在和高度特异性记忆 B 细胞的产生是体液免疫反应的公认特征。生发中心（GC）的特殊微环境可能是这些途径的关键，特别是滤泡树突细胞（FDC）长时间保留免疫复合物（IC）形式的免疫原性抗原的能力。有人提出，这种形式的抗原既能在初次免疫反应期间驱动高亲和力 B 细胞受体体细胞突变体的选择，又能在此后的较长时间内维持记忆 B 细胞区室的稳定性。缺乏激活 Fc 受体 FcgammaRI 和 FcgammaRIII 的小鼠表现出显着增强的 IC 沉积和 FDC 上的保留。然而，这不会导致初级免疫反应的扰动。在目标 1 中，我们建议测试以下假设：这种增强的 IC 沉积和 FDC 保留将导致骨髓中持续性血清抗体、记忆 B 细胞和抗体形成细胞 (AFC) 水平升高。我们还将确定 FDC 上 IC 的保留对于随后使用第二种抗原的免疫是否稳定，以及当 FDC 上的同源抗原水平较高时，持续血清抗体的亲和力是否较低。 IC 与抗原特异性 B 细胞通过抑制性 FcR、FcgammaRIIB 直接相互作用，也可调节记忆生成和维持过程中的 B 细胞活性。缺乏该 FcR 的小鼠在免疫后表现出血清抗体和 AFC 水平升高，这与这一想法以及过去对该 FcR 功能的体外研究一致。然而，由于 FcgammaRIIB 是表达最广泛的 FcR，在许多骨髓谱系和 FDC 中发现，因此这一结论仍然是暂时的。在目标 2 中，我们建议检验在 FcgammaRIIB 中观察到的抗体产生表达失调的假设。缺陷小鼠是由于 B 细胞上缺乏这种 FcR。最后，最近的数据表明，BCR-FcgammaRIIB 共连接时 BCR 信号传导的抑制机制是通过将肌醇多磷酸磷酸酶 SHIP 募集到 FcgammaRIIB 细胞质尾部的 ITIM 基序来介导的。 FcgammaRIIB 的突变形式在 ITIM 基序中 Y 变化大于 F 变化，排除了 SHIP 结合所需的 Y 磷酸化，不会介导转染细胞系中 BCR 信号传导的抑制。在目标 3 中，我们建议使用经过改造的小鼠，在 B 细胞区室中表达 FcgammaRIIB Y-大于 F 突变体，来测试 ITIM-SHIP 途径是抑制体内 B 细胞活性所需的唯一 FcgammaRIIB 启动途径的假设。