Binding of anti-factor VIII antibodies to wild-type and modified A2 domain. Immunoprecipitation analysis of antibody-binding to the wild-type A2 domain (W) and the A2 domain with the Arg⁵⁹³ → Cys substitution (M). Sample 1, MoAb CLB-CAg 9; sample 2, control plasma; samples 3 through 6, plasma of patient A from 1992, 1993, 1994, and 1995; and sample 7, plasma of patient B from 1993. At the right side of the figure the molecular weight marker is depicted.