FIG 1.

Identification of IL-1 receptor antagonist (IL-1RA) as a target of a plasmablast-derived IgG antibody in a patient with IgG4-related disease (IgG4-RD). A, Phylogenetic tree of the plasmablast antibody repertoire from one patient with IgG4-RD. Each peripheral node represents an antibody expressed by a single plasmablast. Red dots indicate clonal family antibodies. Inset: magnification of the branch containing the plasmablast-derived monoclonal antibody (mAb), G4–21. B, Quantification of the binding reactivities of 42 recombinantly expressed mAbs, derived from the plasmablast clonal families of four IgG4-RD patients, against IL-1RA from the human cytokine microarray analysis. C, Quantification of G4–21 binding to the top 25 reactive antigens on the human cytokine microarray. D, ELISA quantification of G4–21 binding to recombinant human IL-1RA, IL-1α or IL-1β and E, additional mAbs G4–05 and G4–25, to IL-1RA. Recombinant human TNFα and BSA, and reactivity of a human IgG secondary antibody alone (E) and an anti-desmoglein 3 (Isotype, α-DSG3) antibody served as a negative control (B – E). Data represent means ± SD of the median fluorescent intensities (MFI) of four replicate spots of each antigen (B and C) or of europium counts of triplicate wells (D and E). ***P<0.001 by two-tailed unpaired Student’s t tests.