General structure and heterogeneity of immunoglobulins

Abstract

The general configuration of immunoglobulins and the chemical relationships that exist between different classes of antibodies have become clear during recent years. On the other hand, the structural features which determine various biological activities of these complex molecules have not been elucidated and, in particular, the basis of combining specificity is not understood. The problem of relating biological activity to chemical structure is complicated by the size of antibody molecules (molecular weight 150 000 or more) and more particularly by the remarkable heterogeneity of their constituent peptide chains. As a result of this complexity, variations in the structure of immunoglobulins cannot be ascribed with certainty to particular biological properties and it has proved impossible to establish the detailed chemical structure of specific antibodies. These difficulties have stimulated renewed interest in the proteins found in multiple myelomatosis and certain related pathological conditions. Individual myeloma proteins have the same general configuration as antibody molecules, but their peptide chain structure is sufficiently homogeneous to permit of detailed chemical analysis. In this paper the general structure of different classes of antibody will be described and their peptide chain structure compared with that of myeloma proteins; several detailed reviews of this subject have been published recently (Cohen & Porter 1964; Franklin 1964; Nisonoff & Thorbecke 1964; Fleischman 1966).