title: The cerebrospinal fluid immunoglobulin transcriptome and proteome in neuromyelitis optica reveals central nervous system-specific B cell populations.
abstract: BACKGROUND
  Neuromyelitis optica (NMO) is a severe demyelinating disorder of the central nervous system (CNS) associated with the presence of an autoimmune antibody response (AQP4-IgG) against the water channel aquaporin-4 (AQP4). It remains unclear whether pathologic AQP4-IgG in the CNS is produced entirely by peripheral plasma cells or is generated in part by infiltrating B cells. To determine the overlap of AQP4-IgG idiotypes between the CNS and periphery, we compared the immunoglobulin G (IgG) transcriptome of cerebrospinal fluid (CSF) plasmablasts with the CSF and serum IgG proteomes in 7 AQP4-seropositive NMO patients following exacerbation.
  
  
  METHODS
  CSF variable region Ig heavy- (VH) and light-chain (VL) transcriptome libraries were generated for each patient from CSF plasmablasts by single cell sorting, reverse transcriptase polymerase chain reaction (RT-PCR), and DNA sequencing. Recombinant antibodies were generated from clonally expanded, paired VH and VL sequences and tested for AQP4-reactivity by cell-binding assay. CSF and serum IgG fractions were searched for sequences that matched their respective CSF IgG transcriptome. Matching peptides within the same patient's CSF and serum IgG proteomes were also identified.
  
  
  RESULTS
  In each NMO patient, we recovered CSF IgG VH and VL sequences that matched germline-mutated IgG protein sequences from the patient's CSF and serum IgG proteomes. Although a modest variation was observed between patients, the overlap between the transcriptome and proteome sequences was found primarily, but not exclusively, within the CSF. More than 50% of the CSF IgG transcriptome sequences were exclusively found in the CSF IgG proteome, whereas 28% were found in both the CSF and blood IgG proteome, and 18% were found exclusively in the blood proteome. A comparable distribution was noted when only AQP4-specific IgG clones were considered. Similarly, on average, only 50% of the CSF IgG proteome matched corresponding peptide sequences in the serum.
  
  
  CONCLUSIONS
  During NMO exacerbations, a substantial fraction of the intrathecal Ig proteome is generated by an intrathecal B cell population composed of both novel and peripherally-derived clones. Intrathecal CSF B cell clones may contribute to NMO disease exacerbation and lesion formation and may be an important target for preventative therapies.
authors.affiliation: Department of Neurology, 12700 E. 19th Ave, Box B-182, Aurora, CO, 80045, USA. markus.kowarik@gmail.com.
authors.forename: Markus C
authors.initials: MC
authors.lastname: Kowarik
authors.affiliation: Department of Biochemistry, University of Colorado Denver, Denver, CO, USA. MONIKA.DZIECIATKOWSKA@UCDENVER.EDU.
authors.forename: Monika
authors.initials: M
authors.lastname: Dzieciatkowska
authors.affiliation: Department of Neurology, 12700 E. 19th Ave, Box B-182, Aurora, CO, 80045, USA. scott.wemlinger@ucdenver.edu.
authors.forename: Scott
authors.initials: S
authors.lastname: Wemlinger
authors.affiliation: Department of Neurology, 12700 E. 19th Ave, Box B-182, Aurora, CO, 80045, USA. alanna.ritchie@ucdenver.edu.
authors.forename: Alanna M
authors.initials: AM
authors.lastname: Ritchie
authors.affiliation: Department of Neurology, TU-München, Klinikum Rechts der Isar, Munich, Germany. hemmer@lrz.tum.de.|Munich Cluster for Systems Neurology (SyNergy), Munich, Germany. hemmer@lrz.tum.de.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hemmer
authors.affiliation: Department of Neurology, 12700 E. 19th Ave, Box B-182, Aurora, CO, 80045, USA. Greg.Owens@ucdenver.edu.
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Owens
authors.affiliation: Department of Neurology, 12700 E. 19th Ave, Box B-182, Aurora, CO, 80045, USA. jeffrey.bennett@ucdenver.edu.|Department of Ophthalmology, Neuroscience Program, Denver, CO, USA. jeffrey.bennett@ucdenver.edu.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Bennett
mesh_terms: D000595:Amino Acid Sequence; D051401:Aquaporin 4 / Q000276:immunology*; D001402:B-Lymphocytes / Q000378:metabolism*; D002490:Central Nervous System / Q000473:pathology*; D016208:Databases, Factual / Q000706:statistics & numerical data; D005434:Flow Cytometry; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000134:cerebrospinal fluid*; D007143:Immunoglobulin Heavy Chains / Q000134:cerebrospinal fluid; D007147:Immunoglobulin Light Chains / Q000134:cerebrospinal fluid; D013058:Mass Spectrometry; D009471:Neuromyelitis Optica / Q000134:cerebrospinal fluid* / Q000473:pathology*; D020543:Proteome; D059467:Transcriptome
chemical_list: C496030:AQP4 protein, human; D051401:Aquaporin 4; D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D020543:Proteome