Studies on Apolipoprotein D a New Protein Moiety of the Human Plasma Lipoprotein System

Abstract

Studies on the human plasma lipoprotein system have demonstrated its antigenic heterogeneity (Aladjem et al., 1957). The basis for this heterogeneity has been clarified by the isolation and characterization of several antigenically distinct polypeptides: A-I, A-II, C-I, C-II, C-III and LP-B (Shore and Shore, 1968; Brown et al., 1969; Alaupovic et al., 1972). A previously uncharacterized determinant designated as “thin-line” polypeptide occurs primarily in HDL (Ayrault-Jarrier et al., 1963) but its presence has also been demonstrated in LDL (Lee and Alaupovic, 1970) and VHDL (Alaupovic et al., 1966). When tested by double diffusion analysis, HDL gives two precipitin lines with anti-HDL₃: a thin precipitin line nearer the antigen well due to the “thin-line” polypeptide and a broad precipitin line nearer the antibody well due to LP-A (Alaupovic et al., 1972). This report describes the isolation and partial characterization of the antigenic determinant previously designated as “thin-line” polypeptide.

This study was supported in part by Grant HL-6221 and HL-7005 from the U.S. Public Health Service and by the resources of the Oklahoma Medical Research Foundation.