Cellular localization of pleurocidin gene expression and synthesis in winter flounder gill using immunohistochemistry and in situ hybridization

Pleurocidin is an antimicrobial peptide isolated from winter flounder and has been previously localized to mucous cells of the skin epidermis and the intestine. The present study was designed to determine the cell type involved in pleurocidin gene expression and protein synthesis in gills from the same species. Whole-mount in situ hybridization with a pleurocidin-specific RNA probe and whole-mount immunohistochemistry with an antipleurocidin antibody localized the expression of this gene and the synthesis of its corresponding protein in a population of cells primarily isolated to the non-lamellar portion of the gill filament. Histological techniques allowed the presumptive identification of these cells as eosinophilic granular cells. These observations suggest that pleurocidin is expressed in not one but two distinct populations of cells within the winter flounder, one being an important group of inflammatory cells, the eosinophilic granular cells.