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January 2009 - March 2010

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University of Minnesota Duluth
Medical School Duluth
Department of Anatomy, Microbiology, and Pathology

PI: Richard L. Leino

Unresolved Aspects of Fish Immunity: A Proteomic Study of Rodlet Cells

The world’s fauna are being confronted by environmental changes brought about by problems like global warming, acid rain, and encroachment by humans and domestic animals, including fish farming. These changes, including intensive fish aquaculture, carry with them heightened costs and risks of spread of infectious diseases. Yet little is known about the fish’s first line of defense against such diseases, their innate immune system. Antimicrobial peptides and proteins, e.g., the "defensins,” are an important component of the innate immune system of animals. Some of these compounds have been identified in mammals, amphibians, and invertebrates but they have received only scant attention in fishes. Valuable information about innate immunity of these vertebrates might be gained by examining fishes for antimicrobial molecules. The rodlet cell appears to be one of the principal cells of the innate immune system in most teleost fishes. This project involves: isolating the mysterious and ubiquitous rodlet cells from fish tissues, purifying and sequencing the proteins of their secretory granules, and the comparing the sequenced proteins to other proteins with known functions; testing the antibiotic nature of their secretions for their killing effects on bacteria, fungi, and protozoa using assays designed for small quantities of defensin-like molecules; and performing in vivo assays to determine what factors, e.g., bacterial lipopolysaccharide, may recruit rodlet cells to a particular tissue site or trigger these cells to release their secretory product. These studies should increase understanding of the innate immune system in fish and innate immunity in general, and also could lead to new designs for therapeutic antibiotics.