Teleosts possess mechanism(s) by which they can generate considerable structural diversity within their tetrameric antibody molecules. In salmonids, this diversity is generated through a process of random polymerisation of the constituent monomeric subunits rather than dependency upon isotypic gene diversity. Thus, one gene product can give rise to as many as six different structural forms of immunoglobulin. In contrast to mammals, evidence suggests that this polymerisation process occurs late in the secretory process and not within the endoplasmic reticulum. This assembly process is likely to be important in the generation of teleost antibody functional diversity, thereby potentially simulating isotypy
