IgG subclass distribution in type 3 VWD IgG-positive samples revealed increased IgG4 and IgG3 in the higher titer inhibitor samples. (A) Measured by ELISA, adding type 3 VWD IgG-positive plasma to rVWF and detecting specifically for each subclass, we found IgG1 as the prominent subclass in NN antibody samples, whereas similar amounts of both IgG1 and IgG4 were identified in the neutralizing antibodies. (B) Each pie chart represents 1 of the 8 IgG-positive antibody samples, arranged from highest titer antibody to lowest. If the antibody inhibited VWF binding to FVIII, collagen type III, collagen type IV, or platelet receptor GPIbα (F8B, CB3, CB4, and GPIbM accordingly), it is noted beneath the sample ID and ranked by degree of inhibition using the greater than carrot (>) if multiple activities were neutralized. We observed increased IgG4 composition in all patients associated with CB3 inhibition, which were also the highest titer samples.