"Rainbow trout are one of the most valuable fish species farmed in the European Union, thus knowledge of its immune system is of practical importance. This project is focused on the study of interleukin 2 (IL2), a central cytokine in the regulation of T-cell responses, which stimulates proliferation of these cells and increases cytotoxicity of CD8+ T cells, natural killer, B cells, monocyte/macrophages and neutrophils. IL2 is an important adjuvant for inactivated or subunit viral vaccines in humans and may have a potential role in protection against bacterial and viral diseases. Initially expression studies of IL2 in head-kidney and spleen will be examined by PCR, after administration of different immunostimulants, since this molecule is not constitutively expressed. Next, the activity of the recombinant protein (rIL2) will be established. An antibody to IL2 will also be generated for subsequent use in ELISPOT assays. Thus the specific cell-mediated immune response in trout will be quantified by enumerating the number of cells secreting IL2 in response to antigen, establishing a relationship between the size of the IL2 response and protection post-vaccination using a model bacterial, Aeromonas salmonicida, and viral, haermorrhagic septicaemia virus, VHSV, pathogen. Further experiments will be carried out using the rIL2 to increase the effectiveness of fish vaccines by inclusion in the vaccine. Following vaccination, the A. salmonicida and VHSV antibody titres will be determined for the serum and correlations sought between the size of the antibody response, the IL2 secreting cell response and resistance. Finally, IL2 secreting cells will be induced and identified using the monoclonal antibodies to detect intracellular IL2 and sorted by FACS. The sorted cells will be characterized in terms of their transcriptome, by microarray analysis. The arrays will also be used with RNA from cells stimulated with rIL2 to get an overview of genes affected in target cells."