The VH Repertoire of a Marsupial (Monodelphis domestica)

Robert D. Miller, Hilary Grabe, and George H. Rosenberg

Abstract:
When contrasted with information available for placental mammals, very little is known of the development of immunocompetence in marsupials. Marsupials, however, provide interesting immunology problems since most appear to be born at a stage of development much less mature than that of placental mammals. To further understand the marsupial immune system, the Ig repertoire of the short tailed opossum Monodelphis domestica was characterized. Majority of the VH clones were isolated in an unbiased manner by screening a spleen cDNA phage library using constant region probes or anchored PCR using constant region specific primers paired with vector specific primers. Analysis of 54 unique VH sequences from this marsupial revealed the presence of two VH families used in the expressed Ig repertoire. The larger family contributed the majority of the clones identified and appears to be derived from 10 to 12 germline VH segments. The second family of clones is derived from a single germline VH. Both VH families are related to the group III sequences described in other vertebrates. Unusual codon bias differences between the two families may result in very different patterns of somatic mutation within the opossum Ig repertoire.