Single Cell Immunophenotyping of Lyme Erythema Migrans Identifies IgM-Switched Memory B Cells (10X Single-Cell Gene Expression)

Erythema migrans (EM) is a skin lesion caused by the spirochete B. burgdorferi (Bb) and is a hallmark initial sign of Lyme disease. Previous studies have demonstrated that T cells and innate immune cells mediate local inflammatory cytokine production that promote the reaction. Despite the established importance of B cells and antibodies in preventing Bb infection and resolving disease, the role of B cells in the skin immune response to Bb is incompletely defined. In this study, we characterized the immunophenotype of EM lesions and used single cell RNA-Seq to investigate B cell receptor (BCR) and T cell receptor (TCR) repertoires in the EM skin lesions and peripheral blood of patients with Lyme disease. We hypothesized that B cells from the circulation, potentially primed by exposure to Bb antigens in regional draining lymph nodes, are recruited into EM lesions and play an active role in the local response to infection. We found that B cells are more abundant in the EM lesion in comparison to autologous uninvolved skin and possess distinct characteristics, including abundant expression of MHCII genes and preferential IgM isotype usage. A subset exhibited low levels of somatic hypermutation despite a gene expression profile more consistent with memory than naïve B cell subsets. Moreover, infiltrating B cells were clonally expanded and a large fraction could be directly traced to circulating relatives. By leveraging single cell gene expression with paired BCR and TCR repertoire sequencing, we demonstrate, for the first time, that B cells are recruited to the skin infection site in early Lyme disease and express a phenotype suggesting that they could play a role in local antigen presentation and antibody production. Six subjects were studied, all with confirmed cases of Lyme Disease. Five of six had samples from both EM rash and unaffected skin. One subject had sample only from EM rash. One subject had an additional PBMC sample. UPDATE [Apr-27-2025] The .rds file was replaced.

游走性红斑（Erythema migrans, EM）是由伯氏疏螺旋体（B. burgdorferi, Bb）引发的皮肤病变，为莱姆病（Lyme disease）标志性的初始体征。既往研究证实，T细胞与固有免疫细胞可介导局部炎性细胞因子的产生，进而促发该病变反应。尽管学界已明确B细胞与抗体在预防Bb感染及缓解疾病进程中的关键作用，但B细胞在针对Bb的皮肤免疫应答中所扮演的角色仍未完全阐明。本研究对EM病变的免疫表型进行了系统表征，并借助单细胞RNA测序（single cell RNA-Seq）分析了莱姆病患者EM皮肤病变与外周血中的B细胞受体（B cell receptor, BCR）及T细胞受体（T cell receptor, TCR）库。我们提出假说：循环中的B细胞或经区域引流淋巴结内Bb抗原致敏后，被募集至EM病变部位，并在针对感染的局部免疫应答中发挥主动作用。研究结果显示，相较于自体未受累皮肤，EM病变内的B细胞丰度更高，且具备独特的表型特征，包括高表达MHC II类基因以及优先使用IgM同种型。其中一个B细胞亚群的体细胞高频突变水平较低，但其基因表达谱更贴近记忆性B细胞亚群而非初始B细胞亚群。此外，浸润至病变部位的B细胞呈现克隆扩增状态，其中相当一部分可直接追溯至循环中的同源B细胞。本研究通过整合单细胞基因表达数据与配对的BCR及TCR受体库测序结果，首次证实：在莱姆病早期，B细胞会被招募至皮肤感染部位，其表达的表型提示它们可能在局部抗原呈递与抗体产生过程中发挥功能。本研究共纳入6名经确诊的莱姆病患者：6名受试者中5名同时获取了EM皮疹与自体未受累皮肤样本；1名受试者仅获取了EM皮疹样本；另有1名受试者额外提供了外周血单个核细胞（peripheral blood mononuclear cell, PBMC）样本。更新 [2025年4月27日]：已替换原.rds文件。