Dimers and trimers of immunoglobulin G covalently cross-linked with a bivalent affinity label

Abstract

A bivalent affinity label, bis(.alpha.-bromoacetyl-.epsilon.-2,4-dinitrophenyllysylproline)ethylenediamine, was synthesized. Treatment of [rabbit] anti-2,4-dinitrophenyl antibodies with this compound produces a mixture of covalently and noncovalently cross-linked material. Only specific antibodies are covalently cross-linked, suggesting that covalent attachment occurs in the variable regions. Covalently cross-linked dimers and trimers were isolated from the reaction mixture in a high state of purity, in yields of about 12 and 4%, respectively. The complexes are stable in solutions containing 10-4 M hapten and can therefore be used as sensitive probes of immune effector functions.