III - Immunology of Amphibians

Abstract

This chapter focuses on the immunological system of amphibians, which, because of their key position in vertebrate evolution, represent important models for the developmental and comparative analysis of the immune system. Amphibians possess B cells and T-like cells in the blood, and it has been demonstrated that these cells are fully mature and can efficiently collaborate in vitro in a “major histocompatibility complex” (MHC)-restricted manner for the production of antibodies to T-cell-dependent antigens. The MHC class I and class II proteins initiate immune responses by presenting foreign peptides to T cells. MHC genes have been characterized in X. laevis and in the axolotl. Most genes were identified in Xenopus by the immunoscreening of a cDNA expression library by using alloantibodies, or by polymerase chain reaction (PCR) in the axolotl using degenerated oligonucleotides that allowed the cloning of genes with low similarity to mammalian homologues. The tissue distribution of MHC class I and class II molecules in adult amphibians is essentially the same as in mammals, as assessed by Northern blotting, immunofluorescence, and immunoprecipitation experiments.