Characterization of immune receptors in fish

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One of the most important roles of the immune system is to prevent the growth of infected or damaged host cells. For example, cells infected with viruses or those found within tumors are recognized as abnormal and efficiently destroyed by specialized white blood cells called lymphocytes. Without this recognition system viral infections and malignant tumors would spread throughout the body. Therefore, understanding how lymphocytes determine if a cell should be killed or spared has been the focus of intense research over the years. These experiments demonstrated that lymphocytes use an intricate network of cell surface proteins to survey surrounding cells for signs of infection or damage. These proteins (or receptors) often recognize a common protein presented on the surface of neighbouring cells, which is reduced or lost once a cell becomes infected or transformed by cancer. Loss of this protein then marks these cells as abnormal and they are subsequently targeted for destruction. This essential mechanism is well studied in humans and mice but little is known in other vertebrate species that encounter viruses and must limit the spread of cancerous cells. Therefore, I am interested in understanding how fish immune cells mediate these important immune responses. Fish lymphocytes function in a similar manner as their mammalian counterparts but the identification and characterization of the immune receptors that regulate these responses is lacking. Recently, I identified a new family of immune receptors in the channel catfish that are related to receptors in mammals involved in immune surveillance for virally infected or cancerous cells. Characterization of these unique catfish receptors represents an excellent opportunity to study the evolution and function(s) of innate immunoregulatory receptors. This will not only enhance our present understanding of fish immune responses but will also provide important information regarding innate immune receptor protection mechanisms throughout vertebrates. Catfish are also a valuable aquaculture crop and a further understanding of their anti-viral and anti-tumor defense mechanisms will allow for improvements of fish health in aquaculture practices.