The main focus of my research is developmental and comparative immunology using the South African clawed frog, Xenopus laevis , as an experimental model. Understanding the immune defense mechanisms of amphibians has taken on increased importance in recent years because of the problem of global amphibian declines. Currently, my laboratory is pursuing two projects. The first project involves the interactions of the developing endocrine system and immune system. The pattern of immune responses in the tadpole is distinct from that of the adult.
Metamorphosis involves a major reorganization of the immune system as well as other organ systems.
We have shown that there is a complete turnover of thymic lymphocytes associated with metamorphosis, and T cells developing in the postmetamorphic frogs have a different phenotype. Lymphocyte expansion and development of T cells with an adult phenotype are dependent on thyroid hormones. We have shown that corticosteroid hormones are involved with the deletion of tadpole T cells that could promote a destructive autoimmune response to new adult antigens that appear at metamorphosis. Studies are underway to support this hypothesis. The second project is to do research on the role of antimicrobial peptides derived from amphibian skin in defense against bacterial, viral, and fungal pathogens associated with global amphibian declines.