Direct evidence for a β₁-adrenergic receptor–directed autoimmune attack as a cause of idiopathic dilated cardiomyopathy
J. Clin. Invest. Roland Jahns, et al. 113:1419 doi:10.1172/JCI20149 [Go to this article.]

Figure 2
Immunological and functional properties of rat anti–β₁-EC_II. (A) ELISA immunoreactivities of different rat and rabbit Ab’s (see key) with peptide antigens corresponding to selected domains of the β₁- or β₂-AR (N terminus (N); C terminus (C); and EC_II-domain (EC_II)) (14). (B) IFM with unfixed (IgG diluted 1:200) or (C) Western blots (IgG diluted 1:2,000) with lysates of Sf9 insect cells expressing recombinant human β₁-AR, β₂-AR, or the WT vector. (D) IFM colocalization experiments with HEK 293 cells transiently expressing β₁-AR, β₂-AR, or flag-tagged AT_1a receptors (IgG diluted 1:200). Examples given are representative for IgG from β₁-EC_II–injected rats and a GST-injected rat (control); domain and β₁-AR/β₂-AR subtype-specific rabbit Ab’s (27) and a monoclonal mouse anti–AT_1a flag Ab (28) served to immunostain the corresponding receptors (β₁-AR, β₂-AR, and AT_1a receptor). (E) Increases in basal (–isoprenaline) or isoprenaline-stimulated (+10 ∝M/l isoprenaline) cAMP levels in Chinese hamster fibroblasts expressing human β₁-AR (CHW-β₁ cells) upon incubation with rat IgG (100 ∝g/ml). Columns represent amount of accumulated cAMP plus or minus SEM (error bars) obtained without (white, control) or in the presence of IgG from rats negative (light gray, GST/NaCl injected) or positive for functionally active anti–β₁-EC_II (black, β₁-EC_II injected). The stimulatory effects of anti–β₁-EC_II were blocked by 5 ∝M bisoprolol, a β₁-selective receptor antagonist (dark gray). **P < 0.001 (ANOVA and Scheff– F post hoc test).