title: Analysis of the 3' Cmu region of the rabbit Ig heavy chain locus.
abstract: The immunoglobulin D (IgD) antibody class was, for many years, identified only in primates, rodents and teleost fish. The limited distribution of IgD among vertebrates suggested that IgD is a functionally redundant antibody class that has been lost by many vertebrate species during evolution. The recent identification of IgD in artiodactyls, however, suggests that IgD might be more widely expressed among vertebrates than previously thought, possibly serving a unique role in immunity. IgD expression has been searched for but not detected in rabbits. In order to search directly for a rabbit Cdelta locus encoding the constant region of IgD, we determined the nucleotide sequence of 13.5 kb of genomic DNA downstream of the rabbit Cmu locus. We did not find a rabbit Cdelta locus in this region, but found instead that this region is densely populated by repetitive elements, including a long interspersed DNA element repeat, six C repeats, and two processed pseudogenes. We conclude that the rabbit probably does not express IgD because there is no Cdelta locus immediately downstream of the rabbit Cmu locus.
authors.affiliation: Department of Microbiology and Immunology, Stritch School of Medicine, Loyola University Chicago, 2160 South First Avenue, Maywood, IL 60153, USA.
authors.forename: Dennis K
authors.initials: DK
authors.lastname: Lanning
authors.forename: Shi-Kang
authors.initials: SK
authors.lastname: Zhai
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Knight
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004742:Enhancer Elements, Genetic / Q000235:genetics; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007148:Immunoglobulin mu-Chains / Q000235:genetics*; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D011544:Pseudogenes / Q000235:genetics; D011817:Rabbits; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D020086:Short Interspersed Nucleotide Elements / Q000235:genetics
chemical_list: D007143:Immunoglobulin Heavy Chains; D007148:Immunoglobulin mu-Chains; D004247:DNA