Quantitative determination of human plasma apolipoprotein A-II by a non competitive enzyme-linked immunosorbent assay

A noncompetitive enzyme-linked immunosorbent assay (ELISA) for apolipoprotein A-II (ApoA-II) was developed. Microtiter plates were coated with affinity purified antibodies to ApoA-II. After incubation with human plasma, the amount of ApoA-II bound to the coated plate was determined with peroxidase-labeled antibodies to ApoA-II. When pure ApoA-II or delipidated reference plasma was used as standard, a single step delipidation was required in order to unmask some antigenic sites of ApoA-II. However, the underestimated ApoA-II values in untreated samples were shown to be corrected by using intact reference plasma as secondary standard. The average concentration of ApoA-II in normolipidemic plasma was 0.376 g/l.