Radioimmunoassay for creatine kinase isoenzymes.

Creatine kinase has three isoenzymes designated MM, MB, and BB, with BB being the grain form and MM the muscle form. Antibodies to BB creatine kinase were obtained by immunization of rabbits with human BB creatine kinase. The antibodies demonstrated specificity for BB and MB creatine kinase (myocardial isoenzyme) but no cross-reactivity with MM creatine kinase. With the use of this antibody, a highly sensitive radioimmunoassay capable of measuring picomolar amounts of MB creatine kinase has been developed. Clinical application of this method should provide a sensitive and specific test for the diagnosis of myocardial infarction.