[Evolution of the immunoglobulins]

Review. All vertebrates, so far tested, possess immunoglobulins of IgM class similar to the IgM of mammals in structure and function. On the phylogenetic level of anuran amphibians a low-molecular weight 7S immunglobulin type appears occurring in the representatives of reptiles and birds, too. These 7S immunoglobulins (earlier called IgY-like immunoglobulins) show physico-chemical and antigenic properties common to the mammalian IgA. Therefore, they can be considered the precursors of mammalian IgA. The immunoglobulins of IgG, IgD, and IgE classes represent phylogenetically modern molecules appearing during the evolution on the level of mammals. Besides, some special developments can be observed amongst the immunoglobulins.