The proposed research will use the crayfish (Procambarus clarkii) to address the role of fixed cells in the recognition of proteins, viruses, bacteria and red blood cells. It will begin to test the hypothesis that a population of fixed cells in the gills of the crayfish is the critical component in the initial recognition and clearance of non-self cells and particles, whereas circulating hemocytes play a secondary, but critical role in the elimination of foreign materials after they are concentrated into the gills. Previous studies with the crayfish, using a unique "transfusion exchange" technique to deplete circulating cells to less than 1% of normal levels in vivo, indicate that the transfused crayfish is quite capable of clearing a wide variety of non-self substances to the gills in a normal manner. In vitro studies indicate, however, that separated populations of granulocytic and agranulocytic hemocytes are capable of recognizing (binding, phagocytosising) bacteria, red blood cells and proteins. The immediate goals of this project will be to define the morphological and functional properties of the fixed cells lining the gill sinuses, i.e. to identify them as podocytes or transiently fixed hemocytes. The results of this research should provide new insights into the mechanisms of non-self recognition and self defense in an invertebrate, the crayfish, apparently lacking lymphocytes and immunoglobulins. The proposed studies also will provide outstanding undergraduate students an opportunity to participate in an ongoing research program, thus promoting their potential for graduate studies in the sciences. In addition this project will continue to enhance the research environment of an undergraduate institution.
