The properties and clinical significance of some electrophoretically slow forms of alkaline phosphatase.

Sera from 8 patients with a marked slow-moving alkaline phosphatase band on electrophoresis were investigated. Inhibitor studies and treatment with neuraminidase showed that all the patients had slow bands with alkaline phosphatase properties resembling those of the liver or bone isoenzyme. In no case did the slow band resemble the intestinal isoenzyme. Immunoelectrophoretic and molecular weight studies indicated that the slow band consisted of an IgG-alkaline phosphatase complex of molecular weight 540 000. Serum from a patient with the slow band was able to bind liver or bone, but not intestinal, alkaline phosphatase from other patients to form the slow band. Serum from patients with the slow band probably contains an abnormal IgG molecule which can bind alkaline phosphatase in the ratio 2:1. No clinical condition was common to all 8 patients although most of them had either intestinal or lung disease.