Immunoglobulins and α1–Acid Glycoprotein Do Not Contribute to the Cholesterol Crystallization—Promoting Effect of Concanavalin A—Binding Biliary Protein

Abstract

Human bile contains cholesterol crystallization-stimulating proteins that can be isolated by concanavalin A-Sepharose chromatography. In the past few years an increasing number of different pronucleating proteins have been identified in the concanavalin A-binding fraction. In this study we attempted to estimate the relative contribution of a number of these proteins to total concanavalin A-binding pronucleating activity. For this purpose, concanavalin A-binding glycoproteins were isolated from gallbladder bile samples from 12 patients with gallstones. The role of IgA, IgG and IgM and alpha 1-acid glycoprotein was investigated by means of immunoextraction. No decrease in crystallization-promoting activity was observed after precipitation of more than 98% of the different immunoglobulins. In addition, removal of more than 95% of alpha 1-acid glycoprotein from different concanavalin A-binding fractions had no significant effect on cholesterol crystallization-promoting activity. The influence of fibronectin was estimated by addition of physiological concentrations to a model bile system. At these concentrations fibronectin did not promote crystallization. From these data we conclude that immunoglobulins, alpha 1-acid glycoprotein and probably also fibronectin do not significantly contribute to total concanavalin A-binding activity.