Immunochemical Heterogeneity of Human Plasma Lipoproteins

Abstract

EVIDENCE for the immunochemical heterogeneity of human plasma lipoproteins has recently been presented¹. Several lipoprotein fractions and a non-lipoprotein containing plasma protein fraction were isolated from human plasma by ultracentrifugal methods. Antiserums against lipoproteins were prepared in rabbits. No cross-reaction was observed between anti-lipoprotein serums and the non-lipoprotein - containing plasma protein fraction. By serological absorption of the antiserums, high-density lipoproteins (hydrated density 1.07–1.16 gm./ml.) were found to be distinguishable from low-density lipoproteins (hydrated density less than 1.063 gm./ml.). Differences were observed between the quantitative precipitin behaviour of two low-density lipoprotein fractions, S _f 6 (hydrated density, 1.03–1.04 gm./ml.) and S _f 13 (hydrated density, 1.015–1.03 gm./ml.), and their respective antiserums. By the Oudin agar diffusion procedure², six to eight bands were observed in tubes. Band formation did not, however, proceed in the usual manner. Rather, the formation of a precipitation zone was observed first, and then, within this zone, bands developed.