The genetic control of immunoglobulin synthesis

The only aspects of the genetics of immunoglobulins which will be discussed in this short paper are those which are directly related to the antigenic specificities carried by these proteins, and these have been discussed recently in a more detailed paper (Oudin 1966). Three kinds of antigenic specificities with different genetic meanings may be distinguished and will be considered in immunoglobulins. They may be discussed also in terms of antigenic patterns, that is, in terms of the structures still unknown which are responsible for these antigenic specificities or, in other words, for the combination of the immunoglobulin molecules with antibody molecules; each antigenic pattern is made of an unknown number of specific groups or determinants which may combine with as many antibody molecules. The isotypic specificities are those which are uniform in all individuals of one animal species (Oudin 1960 b ; Dray et al . 1962). Since they were the only kind of antigenic specificity known before 1956, they did not deserve at that time a special denomination. These isotypic specificities make it possible to distinguish several main classes, now termed IgGr, IgM, IgA among the immunoglobulins, in a manner which is probably more convenient and precise than the usage of physico-chemical characters. The isotypic specificities also permit one to distintinguish, within one class, subclasses which are found in all normal individuals of a species. If two immunoglobulin molecules are endowed with somewhat different isotypic specificities, this would seem to imply that the synthesis of these molecules, or rather of at least one of the polypeptide chains which they contain, is controlled by different structural genes.