Expression of apolipoprotein B epitopes in very low density lipoprotein subfractions: studies with monoclonal antibodies. Arteriosclerosis

Epitope expression was studied in both denatured apolipoprotein B (apo B) on Western blots and in intact low density lipoprotein (LDL) and very low density lipopro-tein subtractions VLDL, (S,120-400), VLDL2 (Sf60-120), and VLDL3 (S,20-60) in com-petitive binding immunoassays with the aid of six monoclonal anti-LDL antibodies. The apo B in all lipoprotein fractions was shown to bind to all antibodies, but signifi-cant differences in apo B epitope expression were observed. On the average, the immunoreactivity of VLDL subtractions (expresssed as binding affinity and as relative 125I-LDL displacing potency) decreased with increasing flotation rate. Similarly, VLDL, was less immunoreactive than lipolyzed "remnants " of VLDL, after treatment with bovine milk lipoprotein lipase. The results indicate that, even when lipoprotein frac-tions obtained from the same individual and having the same kind of apo B subspe-cies were compared, significant differences in immunoreactivity occurred due to the modulating effect of other lipoprotein components on apo B epitope expression. (Arteriosclerosis 4:138-146, March/April 1984) The availability of monoclonal antibodies directedagainst apolipoprotein B (apo B) has made sur