Immunoglobulin as the major low density lipoprotein binding protein in plasma

Plasma from normal humans and Chinese hamsters was shown to contain material which binds to low density lipoproteins (LDL). The binding capacity of these plasmas was demonstrated by passive hemagglutination against human LDL-coated red blood cells. The plasmas were fractionated by affinity chromatography, gel filtration and electrophoresis. Immunologic analyses of these fractions showed that IgM and IgA were the major plasma proteins responsible for the LDL binding titers of human and hamster plasmas. The titer of binding protein in diabetic and non-diabetic humans and hamsters was also determined.