Formation of Immunogenic Conjugates

As a rule, simple chemicals which are potent sensitizers are also highly reactive and can readily be shown to form conjugates with proteins in vivo. Those chemicals unable to form covalent bonds with proteins in vitro show no or only a very low incidence of sensitization. The extent to which a simple chemical is reversibly bound to serum proteins such as albumin has no apparent influence on its ability to sensitize. In several instances, the antibodies formed on sensitization with a simple chemical in vivo are specific not for the original compound injected, but for the modified haptenic structure formed on covalent binding to a protein carrier. 

In experimental studies on the formation of antibodies to a hapten-protein conjugate, it appears that the more immunogenic the protein, the better the response. Although proteins are usually the most efficient carriers, polypeptides, polysaccharides, lipid membranes, or even polynucleotides may be sufficient to impart im-munogenicity. In recent years, direct conjugation of simple chemicals to structural elements of cell membranes (especially of monocytes and macrophages) has been thought to play an important role in the induction of sensitization (de Weck 1975 Shearer 1975). The protein carrier or cell membrane structure of the host may contribute to the specificity of the response (partial autoimmunity). 

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