Longitudinal monitoring of antibodies against FVIII present in a healthy individual. Presented are the results of a longitudinal monitoring of antibodies against FVIII, including titers of binding antibodies, differentiated for individual immunoglobulin isotypes and IgG subclasses (A); Bethesda titers of FVIII inhibitors (A-B); and apparent affinities of antibodies, differentiated for individual immunoglobulin isotypes and IgG subclasses (B). Data for titers of antibodies against FVIII include the variation of the method (±1 titer step). Data for apparent affinities include the 95% CI. Presented are Bethesda titers of FVIII inhibitors (BU/mL; filled red diamonds); titers of antibodies against FVIII (IgG1 [open blue circles]); and apparent affinities of FVIII-specific antibody cluster (IgG1 [filled blue bars]).