A solid phase sandwich immunoenzymmetric assay is described for the determination of
apolipoprotein B in
apolipoprotein CII- and/or CIII-containing
lipoproteins (
chylomicron remnants, VLDL, IDL). During a first incubation step the particles containing
apolipoproteins CII and/or CIII are bound to
antibodies against these components, while the
antibodies are immobilised on microtitre plate wells. After washing, anti-
apolipoprotein B is added in a second incubation step. Finally
peroxidase-labelled anti-sheep
IgG reacts with the bound anti-
apolipoprotein B, thus allowing the quantification of complexes containing both B and CII/CIII
apolipoproteins. The amounts of these complexes were correlated with total
cholesterol,
triacylglycerols, HDL- and
LDL-cholesterol,
apolipoproteins AI and B, as well as with age and sex of the subject. A total of 258 individuals was studied, including patients with
lipid metabolism disorders, patients with manifest
coronary heart disease, and healthy controls. The assay described in this article was compared with radial immunodiffusion after pretreatment of samples. The immunoenzymmetric assay was easier and faster to perform and had a lower detection limit than the classical VLDL
apolipoprotein B determination using ultracentrifugation. Furthermore, it could be performed directly on native serum. Most importantly, the study revealed elevated
apolipoprotein CII/CIII-B levels in
coronary heart disease patients of both sexes compared with normal subjects. Furthermore, in male
coronary heart disease patients a negative correlation was found between the concentrations of
apolipoprotein CII/CIII-B and
HDL-cholesterol. These results suggest a delayed VLDL-HDL exchange of
lipids and
proteins in these patients which results in an accumulation of atherogenic
apolipoprotein B-containing VLDL and IDL.