Detection of Vitamin K Deficiency by Use of an Enzyme-Linked Immunosorbent Assay for Circulating Abnormal Prothrombin

Abstract

A monoclonal antibody was raised against an abnormal decarboxylated prothrombin by a cell fusion technique. A cell line which produces an IgG1 murine antibody to the abnormal prothrombin, but not to prothrombin, was selected. Using this antibody an enzyme-linked sandwich immunoassay was developed for the abnormal prothrombin. The detection range was 0.5 .times. 10-1 .apprx. 0.5 .times. 10-3 .mu.g protein of decarboxylated prothrombin and 0.5 .apprx. 0.5 .times. 10-2 .mu.g protein of abnormal prothrombin in vitamin K-deficient subjects. This discrepancy is attributable to a heterogeneity of decarboxylated prothrombin, depending on the number of .gamma.-carboxyglutamic acid residues. The antibody obtained had a higher affinity to a protein possessing less .gamma.-carboxyglutamic acid residues. The assay system developed may be useful for the detection of vitamin K deficiency, since a severe deficiency may result in less .gamma.-carboxyglutamic acid residues in the protein.