The persistence and heterogeneity of factor VIII:C inhibitors as demonstrated by preparative isofocusing

The purpose of this study was to determine if factor VIII:C inhibitors completely disappear during remission and if they recur on exacerbation, are they similar to or different from the original inhibitors? To answer these questions, isofocusing, which separates proteins on the basis of their p/s, was utilized to recover inhibitors from the plasmas of six patients, five nonhemophiliacs with acquired VIII:C inhibitors and the sixth with classic hemophilia. Initially, all plasmas were studied during the presenting hemorrhagic episodes and, subsequently, following the disappearance or recurrence of the inhibitors. Following isofocusing, each fraction was tested for inhibitory activity. The method enabled us to determine that inhibitors to factor VIII:C persisted even when they could not be demonstrated by conventional methods. The inhibitory activity resulted from a composite of inhibitors, each of the group identified by its own p/. In many patients, some peaks persisted throughout the entire interval of study, whereas others disappeared and new ones appeared, suggesting that various groups of cells were capable of producing the inhibitors.