Interaction of LDL, Lp[a], and reduced Lp[a] with monoclonal antibodies against apoB.
Five monoclonal antibodies (2A, 9A, 6B, L3, L7) produced in mice against human apolipoprotein B were investigated by competitive and inhibitive electroimmunoassay (EIA) for their reactivity with low density lipoprotein (LDL), lipoprotein[a] (Lp[a]), and reduced Lp[a]. All of the antibodies reacted with apoB of the different lipoproteins indicated by very similar slopes of the binding curves. None of them gave a positive reaction with apolipoprotein[a]. The amount of apoB required for 50% inhibition of antibody binding varied for the different antibodies and lipoproteins. Antibody 9A showed almost the same affinity for LDL, Lp[a], and reduced Lp[a]. Antibodies 2A and 6B bound about twofold better to LDL and reduced Lp[a] than to untreated Lp[a]. Antibodies L3 and L7 needed nearly threefold higher amounts of Lp[a]-apoB for 50% inhibition of antibody binding than of apoB of LDL and reduced Lp[a]. The amount of apoB required for 50% inhibition of antibody binding was somewhat higher in inhibitive assay than in competitive assay. We suggest that apo[a] covers certain epitopes of apoB in native Lp[a] leading to a reduced reaction with the monoclonal antibodies. However, it could also be that the binding of the [a]antigen to apoB via disulfide bridges causes profound conformational changes of the apoB region exposed to the surface.
D000293:Adolescent; D000328:Adult; D000911:Antibodies, Monoclonal / Q000276:immunology; D001055:Apolipoproteins B / Q000276:immunology*; D004587:Electrophoresis, Agar Gel; D000939:Epitopes; D006801:Humans; D007122:Immunoelectrophoresis; D017270:Lipoprotein(a); D008074:Lipoproteins / Q000032:analysis*; D008077:Lipoproteins, LDL / Q000276:immunology*
D000911:Antibodies, Monoclonal; D001055:Apolipoproteins B; D000939:Epitopes; D017270:Lipoprotein(a); D008074:Lipoproteins; D008077:Lipoproteins, LDL