B cell repertoire expansion occurs in meningeal ectopic lymphoid tissue
Klaus Lehmann-Horn, Sheng-zhi Wang, Sharon A. Sagan, Scott S. Zamvil, H.-Christian von Büdingen
Klaus Lehmann-Horn, Sheng-zhi Wang, Sharon A. Sagan, Scott S. Zamvil, H.-Christian von Büdingen
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Research Article

B cell repertoire expansion occurs in meningeal ectopic lymphoid tissue

Abstract

Ectopic lymphoid tissues (ELT) can be found in multiple sclerosis (MS) and other organ-specific inflammatory conditions. Whether ELT in the meninges of central nervous system (CNS) autoimmune disease exhibit local germinal center (GC) activity remains unknown. In an experimental autoimmune encephalomyelitis model of CNS autoimmunity, we found activation-induced cytidine deaminase, a GC-defining enzyme, in meningeal ELT (mELT) densely populated by B and T cells. To determine GC activity in mELT, we excised meningeal lymphoid aggregates using laser capture microscopy and evaluated B cell repertoires in mELT and secondary lymphoid organs by next-generation immune repertoire sequencing. We found immunoglobulin heavy chain variable region sequences that were unique to mELT and had accumulated functionally relevant somatic mutations, together indicating localized antigen-driven affinity maturation. Our results suggest that B cells in mELT actively participate in CNS autoimmunity, which may be relevant to mELT in MS and ELT in other chronic inflammatory conditions.

Authors

Klaus Lehmann-Horn, Sheng-zhi Wang, Sharon A. Sagan, Scott S. Zamvil, H.-Christian von Büdingen

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Figure 7

Ig lineage trees evidence intrinsic affinity maturation in mELT.

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Ig lineage trees evidence intrinsic affinity maturation in mELT. (A) IgG...
(A) IgG lineage tree from mELT from Th×2D2 EAE mouse A20. (B) IgG and IgM lineage tree from mELT from Th×2D2 EAE mouse A22. (A and B) Each node represents all sequencing reads with an identical CDR1-CDR3 region. To reduce the risk that rare sequencing errors result in false nodes, only those nodes with ≥3 identical sequences are shown. Dark blue (IgG) or red (IgM) nodes are sequences found exclusively in mELT. Turquoise (IgG) or pink (IgM) nodes are sequences found in mELT and one or more peripheral compartments (blood, spleen, LN). Shared nodes; mELT, peripheral compartments. Black nodes highlighted with a green circle represent the germline sequence (knockin Ig-VH). Gray nodes represent sequences that were not found in the sequencing data but were computed to complete the tree (internal nodes). The size of each node correlates with the number of identical sequencing reads. Two nodes connected by a line differ from each other by one particular nucleotide mutation (if not indicated differently by a number) in a specific position of the entire CDR1–CDR3 region. In A, sequences that were selected for subsequent cloning and expression are labeled (e.g., “H1”) and highlighted with a red circle. (C) Nodes in the IgG lineage trees of 5 Th×2D2 EAE mice were categorized into groups according to the number of mutations relative to the germline sequence (1, 2, 3, 4, 5, ≥6 mutations). For each category, the mean percentage ± SEM of nodes that were found either exclusively in mELT or that were found in mELT and one or more peripheral compartments (blood, spleen, LN) is given. Shared nodes; mELT, peripheral compartments. *P ≤ 0.05; **P ≤ 0.01; Kruskal-Wallis test with Dunn’s multiple comparisons test. mELT, meningeal ectopic lymphoid tissue; EAE, experimental autoimmune encephalomyelitis; CDR, complementarity determining region; LN, lymph node; VH, heavy chain variable region.