title: Toll-like receptor 9 activation induces expression of membrane-bound B-cell activating factor (BAFF) on human B cells and leads to increased proliferation in response to both soluble and membrane-bound BAFF.
abstract: OBJECTIVE
  Activation of TLR7 and TLR9 and high serum levels of BAFF have been implicated in the pathogenesis of SLE. However, little is known about the effects of TLR9 activation on BAFF expression by human B cells. We investigated the effect of the TLR9 agonist, CpG-ODN 2006, on the expression of BAFF and its receptors BAFF-R, TACI and BCMA, in isolated B cells from healthy donors.
  
  
  METHODS
  We used RT-PCR, flow cytometry and ELISA to investigate the expression of BAFF, and flow cytometry for BAFF-R, TACI and BCMA. Functional assays assessed the responses of resting and CpG-ODN-activated B cells to exogenous soluble and membrane-bound BAFF.
  
  
  RESULTS
  CpG-ODN did not induce BAFF secretion, but increased expression of membrane-bound BAFF on B cells. CpG-ODN also induced the expression of TACI and BCMA, but did not up-regulate BAFF-R expression. In functional studies, CpG-ODN sensitized human B cells to proliferate in response to exogenous BAFF. This effect was inhibited by a blocking antibody against BAFF-R, but was not inhibited by anti-TACI or anti-BCMA antibodies. Membrane-bound BAFF, induced by CpG-ODN, co-stimulated the proliferation of B cells stimulated with anti-IgM in a manner that was dependent on the expression of surface BAFF on the CpG-ODN-treated B cells.
  
  
  CONCLUSIONS
  TLR9 activation induces expression of membrane-bound BAFF on human B cells and leads to increased proliferation in response to both soluble and membrane-bound BAFF. These data extend our understanding of the role of TLR9 activation on human B cells and provide insights into the mechanisms by which TLR9 may participate in the pathogenesis of SLE.
authors: Department of Infection, Immunity and Inflammation, University of Leicester, Leicester LE1 9HN, UK.
authors: Eman Y
authors: EY
authors: Abu-Rish
authors: Yassine
authors: Y
authors: Amrani
authors: Michael J
authors: MJ
authors: Browning
mesh_terms: D000328:Adult; D053264:B-Cell Activating Factor / Q000235:genetics / Q000378:metabolism*; D053265:B-Cell Activation Factor Receptor / Q000235:genetics / Q000378:metabolism*; D053301:B-Cell Maturation Antigen / Q000235:genetics / Q000378:metabolism; D001402:B-Lymphocytes / Q000166:cytology* / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D017931:DNA Primers / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D015870:Gene Expression; D006801:Humans; D008213:Lymphocyte Activation; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051217:Toll-Like Receptor 9 / Q000819:agonists / Q000378:metabolism*; D053303:Transmembrane Activator and CAML Interactor Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D053264:B-Cell Activating Factor; D053265:B-Cell Activation Factor Receptor; D053301:B-Cell Maturation Antigen; C513533:CpG ODN 2006; D017931:DNA Primers; D009838:Oligodeoxyribonucleotides; C108467:TNFRSF13B protein, human; C435926:TNFRSF13C protein, human; C086966:TNFRSF17 protein, human; D051217:Toll-Like Receptor 9; D053303:Transmembrane Activator and CAML Interactor Protein
keywords: B cell; BAFF; BAFF-R; BCMA; CpG-ODN; TACI; TLR9