ABSTRACT
Immunoglobulin (Ig) proteins or antibodies are an indispensable component of the immune system in vertebrates, including fish, linking the innate with the antigen-specific defense against invading pathogens such as viruses, bacteria, and parasites. Antibodies are produced by B-lymphocytes and plasma cells, which exclusively transcribe and translate Ig genes by a complex mechanism of recombination. Most of the initial structural and genetic studies on Ig were performed in the murine and human species. Ig from all species possessing such molecules share some common structural features. The most significant shift in serum Ig concentration occurs with various monoclonal gammopathies such as multiple myeloma, a common neoplasic condition in people, nonhuman primates, dogs, mice, and rats. There are three major serologically and structurally defined determinants that are found on Ig of most of the species that have been studied. These markers are isotypes, allotypes, and idiotypes.
