Studies of salmon phagocytic cells - key cells in cellular immune responses.

We propose to investigate, using functional genomics, the relationship between well-known immunostimulants, activation and function of salmon phagocytic cells. The new input to fish immunology is the use of isolated specific cell populations, especially n eutrophils, a salmonid cell line and phagocytic B-cells. Initially, a global approach using microarray technologies will be pursued in the search for immune related genes induced after immunostimulation of salmon phagocytic cells. A selection of genes wil l be made and specific gene expression profiles induced by different immunostimulants and phagocytosis will be verified by real-time PCR. Following immune stimulation central cell functions will be verified by approved methods, the most central comprising flow cytometry and microscopy. Throughout, we will study isolated and defined phagocytic cell populations including neutrophils, head kidney macrophages, B-cells and a salmonid phagocytic cell line expressing a cell surface marker for dendritic cells. Th is enables us to combine immune gene expression studies with functional phagocyte responses, elucidating potential relationships between expression profiles and specific cell functions. Scientific contribution and relevance: Fish phagocytic cells are a p owerful tool for studies of genes and cellular activities, and due to evolutionary distance between species there are possible differences from similar human and animal cells. This is underlined by the recent findings of phagocytic B-cells in fish and up- regulation of MHC II in granulocytes, suggesting differences in responses to pathogens and vaccines. The phagocytic professional antigen presenting cells are the crucial link between native and adaptive immunresponses being central in T-cell activation. T he lack of basic knowledge on fish immune cell functions is one of the major obstacles in fish health for rational design of vaccines and use of immunostimulants, especially for intracellular pathogens and viruses.