Figure 4.

Neutralization of human anti‐β₁‐aabs from DCM patients by 22‐mer cyclopeptides mimicking β₁EC_II with non‐conserved amino acids (compared with the amino acids constituting the EC_II loop of the β₂‐AR) sequentially replaced by alanine: human anti‐β₁‐aabs (IgG fractions) were pre‐absorbed with the indicated cyclopeptide mutants (40 mol/mol IgG, 4°C, 16 h). Anti‐β₁‐aab‐induced cAMP production was measured in HEK293 cells expressing the native β₁‐AR functionally coupled to a cAMP FRET sensor. (A) Representative recordings of FRET ratios obtained upon addition of anti‐β₁‐aabs prepared from a male DCM patient followed by the maximal signal achieved with 1.0 μM of (−)‐isoproterenol (Iso). (B) Prevention of cAMP stimulation after pre‐absorption of patient anti‐β₁‐aabs. Results are normalized to the values without pre‐absorption. Columns represent mean ± SEM from at least three to four independent experiments with IgG prepared from different exemplary DCM patients (two men and one woman). Differences between the non‐mutated 22 C/C/B‐β₁ cyclopeptide and CP mutations were analysed by one‐way ANOVA with subsequent Dunnett's post‐hoc test for multiple comparisons; *P < 0.05; **P < 0.01; ***P < 0.001. Internal negative control: non‐mutated 22C/C/D‐β₂ (sequence and alignment, see Table S1).