Genetic regulation of immunoglobulin synthesis

The genetics of immunoglobulins (Ig) has been discussed from the standpoint of the determinism of the antigenic specificities of different kinds that they carry: isotypic specificities, which are uniform in all individuals of the same animal species; allotypic specificities, which are not the same in all individuals, but are uniform within groups of individuals; idiotypic specificities, each of which not only is particular to the antibody against one given antigen but is, in addition, variable with individuals. Allotypic variants of the Ig are mainly these: in the rabbit, of the L polypeptide chains (ab group) and of the IgG chains (aa group); in man, of the L chains (Inv system) and of the IgG H chains (Gm system); in the mouse, of the IgG and IgA H chains. The control of the allotypic variants of the IgG H chains is mediated in man and mouse by alleles at several closely linked loci which were distinguished, with the help of myeloma proteins, because of differences in isotypic specificities. In the mouse, these loci are closely linked also to the locus which controls the IgA H chains. Several linked loci are also responsible for the IgG H chains of rabbits, and nearly certainly for their L chains. The cellular aspect of the genetics of immunoglobulins has been reviewed with the main conclusion that each cell seems to be specialized in the synthesis of Ig made of H and L chains of only one allotypic kind. The number of cells specialized in the synthesis of one kind of molecules seems to be proportional to the concentration of these molecules in serum.