Anaphylaxis to protamine sulfate mediated by a complement-dependent IgG antibody.

Anaphylactoid reactions to protamine sulfate have been attributed to its capacity for nonimmunologic mast cell degranulation and/or complement consumption. In the current study, evidence is presented for the occurrence of an immunologic anaphylactic reaction mediated by a complement-dependent IgG skin-sensitizing antibody. A retrospective study of blood component donors given protamine for heparin neutralization revealed that prior exposure to protamine is associated with increased risk of adverse reaction to the drug.