Stable, soluble, model immune complexes made with a versatile multivalent affinity-labeling antigen.

We describe here the synthesis of a family of multivalent affinity-labeling antigens based on the soluble carbohydrate polymer Ficoll. Ficoll was derivatized successively with chloroacetate, ethylenediamine, and glutaric anhydride and finally esterified with 2,4-dinitrophenol. Prior to esterification, the polymer could also be derivatized with tyramine to allow trace iodination and with the monosaccharides galactose or mannose. The numbers of substituent groups could be controlled at several points in the synthesis. The resulting multiple dinitrophenyl esters on a Ficoll or glycosylated Ficoll polymer specifically cross-linked anti-dinitrophenyl antibodies to form covalently cross-linked antigen-antibody complexes. The glycosylated Ficolls were particularly made for studies of the influence of antigen structure on the behavior of immune complexes. The intermediates in the synthesis are suitable for other derivatizations as well. These model immune complexes are stable and soluble, they can be separated by size, and they overcome some of the limitations on the study of complexes imposed by previous techniques of preparing them.