Radioimmunological Characterization of Anti Lithocholic Acid Antisera Elicited by [C-6] Carboxylic Acid N-Succinimidyl Esters as Haptenic Derivatives

Abstract

In order to investigate the antigenic effects of the carboxyl group in the side chain and the bridge length on producing anti lithocholic acid antibody, the immunogens in which bile acid is coupled with bovine serum albumin through propionyloxy or butyryloxy amide linkage at the C-6 position were prepared. The antibodies elicited by these conjugates had low titers but showed a high affinity for lithocholic acid with association constants in the range of 0.42-1.04×10⁸ M^-1. The cross-reactivities of both antisera were essentially the same as that of methyl 6α-hemisuccinyloxylithocholate. These results suggested that the side chain hydrolysis product of the methylated antigen worked as a real antigen in the body.