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 6

CDR3s from IgG transcripts present in mELT feature a pattern of a mutations distinct from that in SLOs.

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CDR3s from IgG transcripts present in mELT feature a pattern of a mutati...
(A–C) Logos depict a graphical representation of the probability of any aa to occur in the 13 aa positions of the IgG-VH CDR3 region, reflecting SHM. The mean probability in (A) mELT and (B) SLO is shown. (C) The germline CDR3 sequence from the 8.18-c5 knockin Ig-VH served as the reference sequence. Amino acid positions are according to IMGT, and letter colors are according to hydrophobicity (hydrophilic, blue; neutral, green; hydrophobic, black). N, N-terminus; C, C-terminus. Those aa positions with significant differences (P ≤ 0.05; permutation test based on 9999 Monte-Carlo resamplings) between mELT and SLO are marked with red boxes in A and B, and the respective aa are highlighted with a red background and arrow in A. (D–F) The probabilities for specific aa to be present in specific positions of the CDR3 in mELT (X-axis) or SLO (y axis) are plotted against each other. (D) CDR3 position 105: replacement of the germline aa alanine with aspartate; (E) CDR3 position 109: conservation of the germline aa threonine; (F) CDR3 position 114: replacement of the germline aa proline with leucine. Data points located to the right of the black line indicate overrepresentation of the specific aa in mELT compared with SLO at this specific position of the CDR3. For mouse A18, there are no data points in F because no leucine was detectable in SLOs, and this mouse had to be excluded from this part of the analysis. *P ≤ 0.05; permutation test based on 9999 Monte-Carlo resamplings. (A–F) All IgG sequences from 5 Th×2D2 EAE mice are included, unless stated otherwise above. SLO = spleen and one inguinal LN combined. CDR, complementarity determining region; mELT, meningeal ectopic lymphoid tissue; SLO, secondary lymphoid organ; VH, heavy chain variable region; SHM, somatic hypermutation; IMGT, International ImMunoGeneTics; EAE, experimental autoimmune encephalomyelitis; LN, lymph node.