Stable model immune complexes produced by bivalent affinity labeling haptens: In-vivo survival

In order to provide a better model system for studying the properties of immune complexes, we have synthesized a family of bivalent affinity labeling haptens, the p-nitrophenyl (PNP)* and 2,4-dinitrophenyl (DNP) esters of dicarboxylic acids. At low protein concentration, these compounds covalently cross-link anti-PNP and anti-DNP antibodies with considerable specificity. The resulting immunoglobulin oligomers can be separated into stable dimers, trimers, and a mixture of heavier oligomers. The in-vivo clearance in rabbits of these oligomers and of oligomers produced by another bivalent affinity labeling hapten [(BADL-pro)₂-EDA] and by a non-specific reagent, dimethylsuberimidate, have been studied. The clearance increased with increasing oligomer size with the dicarboxylic ester-linked immunoglobulin. The in vivo behavior of the other oligomers was irregular. These easily synthesized reagents provide a useful model system for studying some biological properties of immune complexes.