ABSTRACT
Abstract ................................................................................................... 86 4.1 Introduction .................................................................................... 86 4.1.1 Mammalian Relationships and Life History ...................... 87 4.2 Marsupial Postnatal Immunology .................................................. 88 4.3 Marsupial Immunoglobulin Genetics ............................................ 90 4.3.1 Constant Region Isotypes .................................................. 90 4.3.2 Germline Variable Region Diversity .................................. 91 4.3.3 Germline Joined V Genes in the Marsupial Genomes ....... 93 4.3.4 Marsupial Light Chains ..................................................... 94 4.3.5 Postnatal B Cell Ontogeny and Antibody Repertoire
Development ...................................................................... 95 4.4 Monotreme Immunglobulin Genetics ............................................ 98 4.4.1 Monotreme Ig Heavy Chain Genetics ............................... 99 4.5 Conclusions .................................................................................. 100 Keywords .............................................................................................. 101 References ............................................................................................. 101
ABSTRACT
Much of the history of mammalian immunology has focused on only one of the three living lineages of mammals: the eutherians, more commonly called the placentals. This is not surprising given that humans and nearly all economically important mammals are eutherian. This chapter reviews what is known about immunoglobulin genetics in the other two lineages, the marsupials and the monotremes. Marsupials appear to have a fairly minimal complement of heavy chain isotypes and limited variable region diversity. Instead they appear to rely more on light chain complexity for generating a diverse antibody repertoire. Monotremes, in contrast have a more diverse collection of heavy chain isotypes and have retained more heavy chain variable region gene complexity than have the marsupials. Monotremes, more than the other two mammalian lineages have also retained more of the characteristics shared with our reptile-like ancestors. This is true of their immunoglobulin genes in addition as evidenced by a novel heavy chain isotype in the platypus with characteristics of both IgG and IgY.
