Antigen-driven affinity maturation of B cells in meningeal ectopic lymphoid tissue in a model of multiple sclerosis

• Applicant: Privatdozent Dr. Klaus Lehmann-Horn
• Subject Area: Experimental Models for the Understanding of Nervous System Diseases ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2018 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 399311414

In secondary progressive multiple sclerosis (SP-MS) and experimental autoimmune encephalomyelitis (EAE), a model of MS, B cell-rich accumulations of lymphoid cells have been identified in the meninges. These aggregates represent meningeal ectopic lymphoid tissue (mELT). Like secondary lymphoid tissue, ectopic lymphoid tissue is thought to contain germinal centers (GC), where B cells proliferate and undergo somatic hypermutation of their immunoglobulin (Ig) genes. This process of antigen-driven affinity maturation may result in B cell receptors and Igs with increased affinity to their target antigens and possibly enhanced pathogenic potential. Although studies, including our own, suggest that mELT contain GCs, their functionality and relevance to disease progression remains poorly characterized. Here, we propose to investigate whether mELT supports antigen-driven affinity maturation and contributes to disease pathogenesis in murine EAE models of central nervous system (CNS) autoimmunity. We will comprehensively characterize the B cell repertoire in mELT, combining laser capture microscopy and next-generation deep immune repertoire sequencing. mELT repertoires will be compared to repertoires in other lymphoid tissues, including CNS-draining cervical lymph nodes. In parallel, a selection of single B cells from mELT will be analyzed. Matching repertoire sequencing data with single cell analyses will provide a novel approach to identifying paired Ig heavy and light chains from overrepresented B cell clones with an a priori estimation of their “evolutionary” standing. Assuming that they are biologically most relevant, these paired Ig sequences will be cloned and express to test their antigen binding affinity as a measure of antigen-driven affinity maturation. Their pathogenic potential will be assessed in vitro and in vivo. This project will contribute to the understanding of the role of B cells and of mELT in CNS autoimmunity and may help identify novel therapeutic targets in treatment of SP-MS.

• DFG Programme: Research Grants