STUDIES ON THE IMMUNOCHEMISTRY OF HUMAN LOW DENSITY LIPOPROTEINS UTILIZING AN HEMAGGLUTINATION TECHNIQUE* Bx

Immunochemical techniques have been used extensively in studies on the chemistry and metabolism of serum lipoproteins. Several investigators (1-8) have produced antibodies against normal human lipoproteins by the injection of purified lipoproteins into rabbits, or into chickens (9). The antigen-antibody reaction between lipoproteins and their antisera has been demonstrated by precipitation (1-3, 5, 8), complement fixation (2, 3), gel diffusion (1-4, 6-8), and immuno-electrophoresis (6, 10). These investigations have suggested that low density and high density lipoprotein fractions axe immunologieally distinct. However, the immunologic relationships between low density lipoprotein subfractions, the $I 3-9 and Sf 10-400 lipoproteins (11), have not been completely defined, since the immunochemieal studies have been hindered by limitations of the procedures available for fraetionation of low density lipoproteins and lack of immunologic techniques sufficiently sensitive for detection of heterogeneity within lipoprotein fractions low in protein. The immunologic specificity of Sf 3-9 and SS 10-400 lipoprotein subfractions is important since metabolic studies have indicated a precursor-product relationship between the subfractions (12) while determinations of N terminal amino acid residues (13) have demonstrated heterogeneity of the protein component especially within the Sf 10-400 lipoprotein fraction.