Institute of Biology and Immunology of Reproduction, Bulgarian Academy of Sciences, Sofia, Bulgaria.
Department of Medical Genetics, Medical University-Sofia, Sofia, Bulgaria.
Front Immunol. 2022 Apr 13;13:865232. doi: 10.3389/fimmu.2022.865232. eCollection 2022.
The typical anti-phospholipid antibodies (APLA) in the anti-phospholipid syndrome (APS) are reactive with the phospholipid-binding protein β2GPI as well as a growing list of other protein targets. The relation of APLA to natural antibodies and the fuzzy set of autoantigens involved provoked us to study the changes in the IgM repertoire in APS. To this end, peptides selected by serum IgM from a 7-residue linear peptide phage display library (PDL) were deep sequenced. The analysis was aided by a novel formal representation of the Igome (the mimotope set reflecting the IgM specificities) in the form of a sequence graph. The study involved women with APLA and habitual abortions (n=24) compared to age-matched clinically healthy pregnant women (n=20). Their pooled Igomes (297 028 mimotope sequences) were compared also to the global public repertoire Igome of pooled donor plasma IgM (n=2 796 484) and a set of 7-mer sequences found in the J regions of human immunoglobulins (n=4 433 252). The pooled Igome was represented as a graph connecting the sequences as similar as the mimotopes of the same monoclonal antibody. The criterion was based on previously published data. In the resulting graph, identifiable clusters of vertices were considered related to the footprints of overlapping antibody cross-reactivities. A subgraph based on the clusters with a significant differential expression of APS patients' mimotopes contained predominantly specificities underrepresented in APS. The differentially expressed IgM footprints showed also an increased cross-reactivity with immunoglobulin J regions. The specificities underexpressed in APS had a higher correlation with public specificities than those overexpressed. The APS associated specificities were strongly related also to the human peptidome with 1 072 mimotope sequences found in 7 519 human proteins. These regions were characterized by low complexity. Thus, the IgM repertoire of the APS patients was found to be characterized by a significant reduction of certain public specificities found in the healthy controls with targets representing low complexity linear self-epitopes homologous to human antibody J regions.
抗磷脂综合征（APS）中典型的抗磷脂抗体（APLA）与磷脂结合蛋白β2GPI 以及越来越多的其他蛋白靶标反应。APLA 与天然抗体和涉及的自身抗原模糊集的关系促使我们研究 APS 中 IgM 库的变化。为此，我们从 7 个残基线性肽噬菌体展示文库（PDL）中血清 IgM 选择的肽进行了深度测序。该分析得到了一种新颖的 Igome（反映 IgM 特异性的模拟表位集）的正式表示形式的辅助，即序列图。该研究包括 24 例 APLA 和习惯性流产的女性与 20 例年龄匹配的临床健康孕妇进行比较。还将她们的 pooled Igomes（297 028 个模拟表位序列）与来自 pooled 供体血浆 IgM 的全球公共 repertoire Igome（n=2 796 484）和人类免疫球蛋白 J 区中发现的 7 个残基序列集（n=4 433 252）进行比较。pooled Igome 表示为连接序列的图，这些序列与同一单克隆抗体的模拟表位相似。该标准基于以前发表的数据。在生成的图中，可识别的顶点簇被认为与重叠抗体交叉反应性的足迹有关。基于 APS 患者模拟表位差异表达的子图主要包含在 APS 中表达不足的特异性。差异表达的 IgM 足迹也显示出与免疫球蛋白 J 区的交叉反应性增加。在 APS 中表达不足的特异性与在 APS 中表达过度的特异性相比，与公共特异性的相关性更高。与 APS 相关的特异性也与人类肽组密切相关，在 7519 个人类蛋白中发现了 1072 个模拟表位序列。这些区域的特点是低复杂度。因此，发现 APS 患者的 IgM 库的特征是某些公共特异性明显减少，而这些特异性在健康对照组中发现，其靶标代表与人类抗体 J 区同源的低复杂度线性自身表位。
