title: Engagement of the B cell receptor for antigen differentially affects B cell responses to Toll-like receptor-7 agonists and antagonists in BXSB mice.
abstract: Nucleic acid sensors of the Toll-like receptor (TLR) family play a well-established role in the pathogenesis of lupus. This is particularly true for a single-stranded RNA-sensing TLR-7 receptor, as lupus mice lacking TLR-7 show ameliorated disease. Cytosine-guanosine dinucleotide (CpG)-DNA-sensing TLR-9, conversely, has a complex regulatory role in systemic lupus erythematosus (SLE). Much less is known about whether signals through the B cell receptor for antigen (BCR) may affect the ability of B cells to respond to suboptimal TLR-7 agonists and antagonists. We studied this question in prediseased BXSB male and female B cells. We found that male B cells responded more vigorously to numerous TLR-7 ligands and this responsiveness was enhanced further upon co-engagement of the BCR. This synergy was seen primarily with the interleukin (IL)-6 secretion. A number of 32-mer inhibitory oligonucleotides (INH-ODNs) with a nuclease-resistant phosphorothioate backbone were capable of blocking TLR-7, but not BCR-induced B cell activation, with an inhibitory concentration (IC)(50) of approximately 100 nm. Surprisingly, while the presence of a single TGC motif at the 5' end of an ODN did not increase its inhibitory capacity, INH-ODNs containing multiple TGC motifs had greater inhibitory potency. When BCR and TLR-7 were co-engaged, INH-ODNs showed a differential effect on B cell activation. Whereas apoptosis protection and G1-M entry completely escaped suppression, IL-6 secretion remained sensitive to inhibition, although with a 10-fold lower potency. Our results suggest that while TLR-7 antagonists may be considered as lupus therapeutics, simultaneous co-engagement of the TLR-7 and BCR might favour autoreactive B cell survival. This hypothesis needs further experimental validation.
authors.affiliation: Department of Internal Medicine, Carver College of Medicine, The University of Iowa, Iowa City, IA 52242, USA.
authors.forename: T
authors.initials: T
authors.lastname: Layer
authors.forename: A
authors.initials: A
authors.lastname: Steele
authors.forename: J A
authors.initials: JA
authors.lastname: Goeken
authors.forename: S
authors.initials: S
authors.lastname: Fleenor
authors.forename: P
authors.initials: P
authors.lastname: Lenert
mesh_terms: D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D004357:Drug Synergism; D005260:Female; D015850:Interleukin-6 / Q000378:metabolism; D008180:Lupus Erythematosus, Systemic / Q000188:drug therapy / Q000209:etiology / Q000276:immunology; D008297:Male; D008562:Membrane Glycoproteins / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D011947:Receptors, Antigen, B-Cell / Q000819:agonists*; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology*; D013844:Thiazoles / Q000494:pharmacology; D051199:Toll-Like Receptor 7 / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000235:genetics; D051217:Toll-Like Receptor 9 / Q000819:agonists
chemical_list: D000888:Antibodies, Anti-Idiotypic; C551788:CL 075; D015850:Interleukin-6; D008562:Membrane Glycoproteins; D009838:Oligodeoxyribonucleotides; D011804:Quinolines; D011947:Receptors, Antigen, B-Cell; D013844:Thiazoles; C477038:Tlr7 protein, mouse; C495370:Tlr9 protein, mouse; D051199:Toll-Like Receptor 7; D051217:Toll-Like Receptor 9; C044203:anti-IgM