Heterogeneity of human circulating anticoagulants against antihemophilic factor (factor VIII).

The heterogeneity of human circulating anticoagulants against antihemophilic factor (AHF, factor VIII) observed in seven patients, both with and without classic hemophilia, was investigated by neutralization of their activity with antiserums directed to whole IgG and to lambda and kappa light chains. All seven anticoagulants were immunoglobulins. Six appeared to contain both kinds of light chains, although the dual light chain composition of two of these could be demonstrated only at high concentration of antiserum. In one circulating anticoagulant, light chain specificity could not be demonstrated with small amounts of antiserum, and with larger amounts, only lambda light chain specificity was revealed. Whether or not this circulating anticoagulant really contained a single light chain type could not be ascertained with our technique. The evidence presented suggested that circulating anticoagulant antibodies against AHF are polyclonal in nature.