Single-cell immunophenotyping of the skin lesion erythema migrans identifies IgM memory B cells.

Ruoyi Jiang,Khadir Raddassi,David A Hafler,Steven H Kleinstein,Ira Fleming,Kenneth R Dardick,Linda K Bockenstedt,Alex K Shalek,Alexia A Belperron,Ruth R Montgomery,Kenneth B Hoehn,Hailong Meng

doi:10.1172/jci.insight.148035

Abstract

The skin lesion erythema migrans (EM) is an initial sign of the Ixodes tick–transmitted Borreliella spirochetal infection known as Lyme disease. T cells and innate immune cells have previously been shown to predominate the EM lesion and promote the reaction. Despite the established importance of B cells and antibodies in preventing infection, the role of B cells in the skin immune response to Borreliella is unknown. Here, we used single-cell RNA-Seq in conjunction with B cell receptor (BCR) sequencing to immunophenotype EM lesions and their associated B cells and BCR repertoires. We found that B cells were more abundant in EM in comparison with autologous uninvolved skin; many were clonally expanded and had circulating relatives. EM-associated B cells upregulated the expression of MHC class II genes and exhibited preferential IgM isotype usage. A subset also exhibited low levels of somatic hypermutation despite a gene expression profile consistent with memory B cells. Our study demonstrates that single-cell gene expression with paired BCR sequencing can be used to interrogate the sparse B cell populations in human skin and reveals that B cells in the skin infection site in early Lyme disease expressed a phenotype consistent with local antigen presentation and antibody production.

Highlights

Lyme disease (LD), an Ixodes tick–transmitted infection with spirochetes of the Borrelia burgdorferi sensu lato complex, is the most common vector-borne disease in the Northern Hemisphere [2, 3]
The erythema migrans (EM) lesion results from local skin infection with Ixodes tick–transmitted B. burgdorferi spirochetes
The act of tick feeding and the associated immunomodulatory effects of tick saliva disrupt normal wound healing and create a protective niche for B. burgdorferi to establish infection in the blood-meal host skin [22, 23]. This introduction of B. burgdorferi spirochetes at the bite site and their subsequent expansion elicits the first clinical sign of LD, EM, that we sought to elucidate at single-cell resolution

Summary

Introduction

Lyme disease (LD), an Ixodes tick–transmitted infection with spirochetes of the Borrelia burgdorferi sensu lato complex (genus Borreliella; ref. 1), is the most common vector-borne disease in the Northern Hemisphere [2, 3]. A study using a blister technique to extract cells from EM lesions found an increased frequency of T cells in comparison with their prevalence among PBMCs [9]. B cells were found at a frequency that was considerably lower than their prevalence in PBMCs, this could be influenced by the method for cell extraction By flow cytometry, both CD4+ and CD8+ T cells appeared antigen experienced, as assessed by CD45RO and CD27 expression, with enrichment of CD4+ T memory and effector subsets and CD8+ effector/cytolytic subsets. Understanding B cell responses in the EM lesion is key to identifying host factors that may be important determinants of localized versus systemic infection with this extracellular pathogen

Methods

Results

Conclusion