Immunoglobulin genetics of marsupials

Abstract

Until recently, studies of marsupial immunoglobulins were limited to primarily protein analyses, such as Protein A binding and immunological cross-reactivity to eutherian immunoglobulins to draw conclusions about the isotypes present in metatherians. This left an interesting gap in our knowledge of the evolution of vertebrate, more specifically mammalian, antibodies and provided little insight into the diversity of marsupial antibodies. Recently, however, there has been a flurry of papers from multiple laboratories describing, at the molecular level, the heavy and light chain classes present in marsupials with some analysis of the expressed repertoires. These studies have provided the evidence to determine when some of the uniquely mammalian isotypes, e.g. IgG and IgE, appeared in evolution, and are a first look at the complexity of heavy and light chain variable regions in a metatherian. Here we review what was known prior to the cloning of marsupial Ig genes and what we have learned recently.