Effect of fVIII synthetic peptides on antibody binding to immobilized light chain. Increasing concentrations of A3 peptide 1804-1819 were preincubated with IgG from MU (•), RI (▴), MS (▵), or MoAb CLB-CAg A (○) for 1 hour at 37°C, and the mixture (200 μL) was added to the biosensor cuvette containing light chain immobilized as in Fig 4. In the control experiments, binding of MU in the presence of peptide 417-428 (x), amino acids QRIGRKYKKVRF, or the randomized version of 1804-1819 (□) was determined as above. Antibody binding in the presence of peptide is expressed as the percentage of antibody binding when no peptide was added.