title: Pharmacological inhibition of TLR9 activation blocks autoantibody production in human B cells from SLE patients.
abstract: OBJECTIVE
  Toll-like receptor 9 (TLR9), which recognizes hypomethylated DNA [cytosine-phosphate-guanine (CpG)], plays a role in the maintenance of serological memory and has been recently implicated in the pathogenesis of SLE. We previously reported that in vitro TLR9 triggers memory B-cell differentiation into antibody-producing cells, and that the MyD88-inhibitor ST2825 blocks TLR9-induced plasma cell (PC) generation. Here, we investigated whether memory B cells produce autoantibodies in SLE patients with active disease or in clinical remission, and whether ST2825 could inhibit PC generation in SLE patients.
  
  
  METHODS
  Peripheral blood mononuclear cells from 10 SLE patients in clinical remission and 2 with active SLE were cultured in the presence of CpG with or without ST2825. Phenotypical analysis of CpG-stimulated cells was performed by flow cytometry. Supernatants were collected to measure antibody production by ELISA and to detect autoantibodies by IF.
  
  
  RESULTS
  CpG-induced TLR9 stimulation caused autoantibody secretion in patients with active disease and in the majority of patients in clinical remission. Inhibition of MyD88 completely blocked the de novo generation of PCs and the secretion of autoantibodies.
  
  
  CONCLUSIONS
  Autoreactive B cells persist in SLE patients during disease remission in the circulating B-cell memory pool. TLR9-dependent activation of memory B cells by pathogens could be one of the mechanisms triggering relapses in SLE. Compounds targeting the TLR/MyD88 pathway may be used as novel therapeutic tools to treat acute disease and to prevent relapses in SLE patients.
authors.affiliation: Cytometry and B-cell Development Unit, Research Center, Department of Nephrology and Urology, Children Hospital Bambino Gesù, and Department of Public Health and Cell Biology, University of Rome Tor Vergata, Rome, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Capolunghi
authors.forename: Maria M
authors.initials: MM
authors.lastname: Rosado
authors.forename: Simona
authors.initials: S
authors.lastname: Cascioli
authors.forename: Elia
authors.initials: E
authors.lastname: Girolami
authors.forename: Silvia
authors.initials: S
authors.lastname: Bordasco
authors.forename: Marina
authors.initials: M
authors.lastname: Vivarelli
authors.forename: Barbara
authors.initials: B
authors.lastname: Ruggiero
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Cortis
authors.forename: Antonella
authors.initials: A
authors.lastname: Insalaco
authors.forename: Nicola
authors.initials: N
authors.lastname: Fantò
authors.forename: Grazia
authors.initials: G
authors.lastname: Gallo
authors.forename: Eleonora
authors.initials: E
authors.lastname: Nucera
authors.forename: Maria
authors.initials: M
authors.lastname: Loiarro
authors.forename: Claudio
authors.initials: C
authors.lastname: Sette
authors.forename: Rita
authors.initials: R
authors.lastname: De Santis
authors.forename: Rita
authors.initials: R
authors.lastname: Carsetti
authors.forename: Vito
authors.initials: V
authors.lastname: Ruggiero
mesh_terms: D000293:Adolescent; D000328:Adult; D000917:Antibody Formation / Q000276:immunology; D000921:Antibody-Producing Cells / Q000276:immunology / Q000378:metabolism; D001323:Autoantibodies / Q000276:immunology* / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D016022:Case-Control Studies; D018899:CpG Islands / Q000276:immunology; D005260:Female; D006574:Heterocyclic Compounds, 2-Ring / Q000276:immunology; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000276:immunology* / Q000378:metabolism; D008297:Male; D053594:Myeloid Differentiation Factor 88 / Q000276:immunology; D013141:Spiro Compounds / Q000276:immunology; D051217:Toll-Like Receptor 9 / Q000276:immunology* / Q000378:metabolism; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D006574:Heterocyclic Compounds, 2-Ring; C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; C525002:ST2825; D013141:Spiro Compounds; D051217:Toll-Like Receptor 9