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065 CXCL13 levels and autoantibody epitope specificities in LGI1-autoantibody syndromes
  1. Sophia Michael1,2,
  2. Melanie Ramberger1,
  3. Isabel Maria Leite1,2,
  4. Arjune Sen1,2,
  5. Patrick Waters1,
  6. Sarosh Irani1,2
  1. 1John Radcliffe Hospital, Oxford
  2. 2Oxford Autoimmune Neurology Group, University of Oxford

Abstract

CXCL13 triggers B-cell homing to germinal-centres (GCs). Plasma CXCL13 levels are a marker of GC activity, and CSF CXCL13 levels are elevated in MS, NMDA-R-antibody encephalitis, and NMO. Our objectives were to examine CXCL13 concentrations in LGI1-antibody patients, and the concept of GC-reactions in these patients. Additionally, we explored patient serum binding patterns to two LGI1 domains: LRR and EPTP.

End-titrations against full-length LGI1, LRR and EPTP were quantified by live-CBA for 100 sera from 38 LGI1-antibody patients. Serum CXCL13 levels were determined by ELISA in 86 samples from 19 LGI1-antibody patients and HCs (n=20), and evaluated with Mann-Whitney and Spearman’s correlation.

98% sera bound both EPTP and LRR, with tight correlation in end-titres (r 0.9257;p<0.0001****) which did not change over disease course. LGI1- antibody patients showed higher serum levels of CXCL13 compared to HCs (p<0.0001). CXCL13 trends over time showed markedly high levels at onset and sharp rises during relapses.

LGI1-antibody patients showed high CXCL13 levels with dynamic longitudinal fluctuations. Autoantibodies with reactivity to both EPTP- and LRR-LGI1 domains were detected in equal proportions throughout disease, indicating their ongoing production. Overall, these findings suggest that sustained, ongoing GC-reactions may act as a dominant mechanism of autoantibody production in LGI1-antibody syndromes.

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