Two-Site Monoclonal Antibody Assays for Human Heart- and Brain-Type

Monoclonal antibodieshave been raised against human heart- and brain-type creatine kinase (CK-MB and CK-BB). We used a low-affinity monoclonal antibody to develop a simple two-step immunoaffinity purification procedure for native CK-MB. Antibodies of higher affinity were used to construct specific two-site immunoradiometric assays for CK-MB and CK-BB. Inthe assay forCK-MB we used an 1251 labeledB subunit-specificantibodywithan immobilizedanti-M subunit antibody-adding either simultaneously, for a 1-h assay inwhich between 5 and 1000 ng of CK-MB per milliliter couldbe measured withan intra-assayCV of4 % to20%, or sequentially,fora 2-h magnetic separation assay in which between 0.5 and 1000 ng/mL could be measured withan intra-assayCV of 14 to 19%. Inboth versionsCK-BB up to 100 ng/mL and CK-MM up to5000 ng/mL didnotinterfere.I