Immunochemical measurement of lipoprotein X

Abstract

Lipoprotein X, an abnormal lipoprotein that is specific for cholestasis, was quantitated by immunochemical methods. Interfering lipoproteins also present in normal serum and sharing antigenic determinants with lipoprotein X were removed before the sample was applied, by precipitation with purified anti lipoprotein B or a γ globulin fraction of specific lipoprotein B antiserum. On Laurell electrophoresis, peak height was linearly related to lipoprotein X concentration in the range 0.20-10 g/l of serum. Sensitivity could be increased further by staining the plates. The coefficient of variation was less than 5%. Single radial immunodiffusion (Mancini et al. technique) was somewhat less sensitive and accurate. Results were available after 3 hr by Laurell's electroimmunodiffusion technique, and after 72 hr by the technique of Mancini et al. Equivalent results were obtained for samples of lipoprotein X of extrahepatic or intrahepatic origin.