[Application of monoclonal antibodies to the assay of apolipoproteins]

Abstract

Our present understanding of the dyslipoproteinaemias comes mainly from recent advances in our knowledge of the apolipoproteins and their metabolic roles. The concentrations of apo Al and apo B in plasma are accepted to be the best measures of lipoproteins as risk factors for cardiovascular disease. This review describes the advantages and limitations of monoclonal antibodies in the immunoassay of apo Al and apo B. Two different molecular forms of apo B are present in plasma: B-100 secreted by the liver, and the smaller B-48 from the intestine. Some, but not all, of the antigenic sites of B-100 are present on B-48, which allows us to measure all apo B or apo B-100 alone. The expression of some antigenic sites is influenced by the type of lipids present with apo B. These sites are variably expressed across the spectrum of apo-B containing lipoproteins. Some antigenic sites on apo Al vary in their expression but, while lipids have affected the reactivity of apo Al with some polyclonal antisera, our studies with monoclonal antibodies have shown that all antigenic sites are present independently of the presence of lipids. Some antigenic sites are fully expressed on all HDL but the expression of a number of sites increases during storage of samples, and at a rate which depends on the storage conditions, and probably on chemical changes in apo Al. Thus, we can choose to assay either all or only a selection of apo Al and apo B in a plasma sample, according to the antibody and conditions of assay which are chosen.(ABSTRACT TRUNCATED AT 250 WORDS)