title: Immune complexes containing factor V in a patient with an acquired neutralizing antibody.
abstract: An 82-year-old woman presented with extensive hematomas and melena associated with markedly decreased plasma factor V coagulant activity (FV:C). Using a competitive enzyme-linked immunosorbent assay developed in our laboratory, we made serial measurements of factor V antigen (FV:Ag) in plasma and found it to be normal or elevated. The patient's plasma was demonstrated to contain an IgG antibody that could neutralize FV:C in normal plasma. The antibody was of restricted heterogeneity (IgG1, IgG2,kappa). Circulating immune complexes containing antibody to factor V and FV:Ag were demonstrated directly in the plasma by immunoelectrophoresis with polyclonal monospecific antibody and with a monoclonal antibody using an enzyme-linked immunosorbent assay. Presence of neutralizing antibody could be demonstrated in vitro even at times when FV:C was within normal limits by heat inactivation of FV:C. Treatment with plasma and platelet transfusions as well as plasmapheresis induced definite but transient elevation of FV:C. Steroid therapy lowered the neutralizing antibody concentration and produced a rapid and persistent elevation of FV:C during two separate hospitalizations. This report describes a patient in whom levels of FV:Ag have been serially measured, and the presence of circulating immune complexes consisting of factor V and a neutralizing antibody have been directly demonstrated.
mesh_terms: D000368:Aged; D000936:Antigen-Antibody Complex / Q000032:analysis*; D001323:Autoantibodies / Q000276:immunology; D001792:Blood Platelets / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005165:Factor V / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000276:immunology; D005260:Female; D006801:Humans; D007122:Immunoelectrophoresis; D009500:Neutralization Tests
chemical_list: D000936:Antigen-Antibody Complex; D001323:Autoantibodies; D005165:Factor V