Influence of autoantibodies to creatine kinase-BB on assays for MB isoenzyme.
We describe the influence of autoantibodies that bind creatine kinase BB (CK-BB) on the methods for MB isoenzyme. If these autoantibodies are present in patients' sera, they cause the formation of macro CK type 1 (immunoglobulin-linked CK-BB). In some of these cases they can bind not only endogenous CK-BB but also CK-MB without significantly affecting enzyme activity. Although these antibodies show distinctly less affinity for CK-MB than for CK-BB, they nevertheless bind CK-MB in these particular sera, because their concentration exceeds that of CK-BB isoenzyme. If a person with such autoantibodies has an acute myocardial infarction, the immunoinhibition method for CK-MB, which does not discriminate between CK-MB and CK-BB, will recognize the increase and peak of CK-MB with time, although persistent macro CK activity will be superimposed on the typical isoenzyme pattern. However, isoenzyme electrophoresis and recently introduced immunoenzymometric assays for CK-MB in these cases may be less sensitive for detecting myocardial infarctions, because the typical increase in CK-MB activity may be identified later in the progression of symptoms, or even be missed.
D001323:Autoantibodies / Q000032:analysis*; D003402:Creatine Kinase / Q000097:blood* / Q000276:immunology; D005188:False Negative Reactions; D006801:Humans; D007525:Isoelectric Focusing; D007527:Isoenzymes; D008722:Methods; D009203:Myocardial Infarction / Q000201:enzymology
D001323:Autoantibodies; D007527:Isoenzymes; D003402:Creatine Kinase