Donor-specific B cells in Transplantation

摘要 肾移植引发强大的 B 细胞反应，产生针对移植物的特异性抗体 捐助者。 B 细胞对同种异体 HLA（面板反应性抗体，PRA）和移植供体（供体）的反应 特异性抗体（DSA）与排斥和移植物丢失的风险相关，因此可以作为以下疾病的诊断指标： 同种异体免疫。产生 DSA 的 B 细胞反应会引发最令人烦恼的排斥类型（抗体- 介导的排斥反应（ABMR）和慢性 ABMR，因此对治疗方法的开发存在很大兴趣 专门针对 B 细胞。然而，一些 B 细胞反应可能与移植相关甚至促进移植 生存（免疫调节、调节、操作耐受性）。虽然已经有广泛的 血液 DSA 的特异性和功能的研究 对血液 DSA 的特性几乎一无所知 供体特异性 B 细胞。我们提出的研究将首次确定 肾移植受者体内供体特异性 B 细胞反应，以确定相关特性 具有并可能有助于稳定的移植功能，而不是排斥。作为首要目标， 供体特异性 B 细胞反应将通过确定供体的重链和轻链 Ig 序列来研究 通过单细胞测序确定特定 B 细胞，并通过 RNA-seq 确定其表型特征。我们将确定关键 Ig 的特性，例如克隆多样性、体细胞超突变程度或 Ig 独立特性，例如 功能稳定或排斥反应的受者体内产生细胞因子。作为第二个目标，捐赠者特异性 Ig 通过 NGS 获得的序列将在一年以上（最多两年）的时间内进行前瞻性研究。我们会 确定克隆型是否会像 T 细胞预期的那样在预期排斥反应中扩展和多样化 相关反应；以及排斥治疗后供体特异性序列如何变化。我们还将 确定在具有稳定移植物的受者中，供体特异性 B 细胞是否编码具有不同特性的 Igs。作为第三个 目标，我们将首先对关键属性进行调查（例如最大结合力、亲合力、直接 供体细胞的激活和抗原特异性（在可能的情况下，使用移植组织进行确认）重组 对供体细胞进行单克隆 DSA 以确定这些特性是否可以解释 致病性。该研究可能揭示评估风险的新方法和生物治疗的新目标 干预。该研究还可能激发修改移植中 B 细胞反应的合理方法 以个性化的方式向接收者提供信息，目的是促进保护性反应并对抗 致病的。

Abstract Kidney transplantation elicits powerful B cell responses that generate antibodies specific for the transplant donor. B cell responses to allogeneic HLA (panel reactive antibodies, PRA) and to the transplant donor (donor- specific antibodies, DSA) correlate with risk of rejection and graft loss and thus serve as diagnostic indices of allo-immunity. B cell responses that generate DSA initiate the most vexing types of rejection (antibody- mediated rejection, ABMR) and chronic ABMR and hence much interest exists in development of therapeutics that specifically target B cells. Some B cell responses however may correlate with or even promote graft survival (immune regulation, accommodation, operational tolerance). Although there has been extensive investigation of the specificity and function of the blood DSA hardly anything is known about the properties of donor-specific B cells. The research we propose will identify for the first time key characteristics of donor-specific B cell responses in kidney transplant recipients to determine what properties associate with and potentially contribute to stable graft function, as opposed to rejection. As a first objective, donor-specific B cell responses will be studied by determining Heavy and Light chain Ig sequences of donor- specific B cells by single cell sequencing and their phenotypic signature by RNA-seq . We will determine key properties of Ig, such as clonal diversity, extent of somatic hypermutation or Ig independent properties such as production of cytokines in recipients with stable function or rejection. As a second objective, donor-specific Ig sequences obtained by NGS will be studied prospectively over periods > a year (up to two years). We will determine whether clonotypes expand and diversify in anticipation of rejection as would be expected of T cell dependent responses; and how donor-specific sequences change following rejection treatment. We will also determine if in recipients with stable grafts, donor-specific B cells encode Igs with distinct properties. As a third objective, we will conduct the first investigation of key properties (e.g. maximum binding, avidity, direct activation of donor cells and antigen specificity, where possible, confirmed using graft tissues) of recombinant monoclonal DSA on donor cells to determine whether these properties could explain differences in pathogenicity. The research might reveal novel approaches to assessing risk and new targets for biological intervention. The research might also inspire rational approaches to modifying B cell responses in transplant recipients in a personalized manner with the goal of promoting protective responses and antagonizing pathogenic ones.