Serologic characteristics of PRT/H Abs. (A) Representative titration curves of high-titer PRT/H Abs in 19 patients demonstrating antibody titer range of 1:1800 to 1:175 000. (B) Specificity of high-titer PRT/H Abs with PRT/H antibody levels of A450nm >3 (n = 32). Each symbol represents an individual CPB patient. (C) Heparin-dependent binding of PRT/H Abs of patients depicted in B.