Pharmacological inhibition of TLR9 activation blocks autoantibody production in human B cells from SLE patients.
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.
Capolunghi
Federica
F
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.
Rosado
Maria M
MM
Cascioli
Simona
S
Girolami
Elia
E
Bordasco
Silvia
S
Vivarelli
Marina
M
Ruggiero
Barbara
B
Cortis
Elisabetta
E
Insalaco
Antonella
A
Fantò
Nicola
N
Gallo
Grazia
G
Nucera
Eleonora
E
Loiarro
Maria
M
Sette
Claudio
C
De Santis
Rita
R
Carsetti
Rita
R
Ruggiero
Vito
V
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
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