title: Soluble CD27 induces IgG production through activation of antigen-primed B cells.
abstract: OBJECTIVE
  High levels of soluble CD27 (sCD27), a marker of immune activation, are found in several infectious [including human immunodeficiency virus type-I (HIV-1)] and autoimmune diseases; however, a direct biological effect of sCD27 on B cells has not been established. The aim of this study was to investigate whether sCD27, by binding to CD70, can induce immunoglobulin G (IgG) production from B cells.
  
  
  METHODS
  B cells from healthy and HIV-1-infected individuals were cultured with recombinant human sCD27 (rhsCD27), and IgG production was measured. The role of rhsCD27 in inducing the expression of transcription factors involved in plasma cell differentiation was evaluated. Furthermore, we investigated the impact of different cytokines on the modulation of CD70 expression on B cells and the relationship between levels of IgG and sCD27 in serum from healthy and HIV-1-infected individuals.
  
  
  RESULTS
  We demonstrated that rhsCD27 induced IgG production from antigen-primed (CD27+) B cells. This effect was mediated by rhsCD27 binding to CD70 on B cells leading to activation of Blimp-1 and XBP-1, transcription factors associated with plasma cell differentiation. We found a significant correlation between levels of serum sCD27 and IgG in HIV-1-infected individuals and healthy controls.
  
  
  CONCLUSIONS
  sCD27 may act to enhance immunoglobulin production and differentiation of activated memory or recently antigen-experienced B cells, thus providing an activation signal to antigen-experienced B cells. This mechanism may operate during autoimmune and chronic infectious diseases, situations in which continuous immune activation leads to upregulation of CD70 expression and increased sCD27 cleavage.
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: L V P
authors.initials: LV
authors.lastname: Dang
authors.forename: A
authors.initials: A
authors.lastname: Nilsson
authors.forename: H
authors.initials: H
authors.lastname: Ingelman-Sundberg
authors.forename: A
authors.initials: A
authors.lastname: Cagigi
authors.forename: L B S
authors.initials: LB
authors.lastname: Gelinck
authors.forename: K
authors.initials: K
authors.lastname: Titanji
authors.forename: A
authors.initials: A
authors.lastname: De Milito
authors.forename: S
authors.initials: S
authors.lastname: Grutzmeier
authors.forename: J
authors.initials: J
authors.lastname: Hedlund
authors.forename: F P
authors.initials: FP
authors.lastname: Kroon
authors.forename: F
authors.initials: F
authors.lastname: Chiodi
mesh_terms: D000328:Adult; D000368:Aged; D023241:Antiretroviral Therapy, Highly Active / Q000379:methods; D001402:B-Lymphocytes / Q000276:immunology*; D053282:CD27 Ligand / Q000276:immunology; D016022:Case-Control Studies; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D015658:HIV Infections / Q000097:blood* / Q000188:drug therapy; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D008213:Lymphocyte Activation; D008297:Male; D008875:Middle Aged; D060888:Real-Time Polymerase Chain Reaction; D012995:Solubility; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7 / Q000276:immunology*; D055815:Young Adult
chemical_list: D053282:CD27 Ligand; C505771:CD70 protein, human; D007074:Immunoglobulin G; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7