Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: December 20, 2007
Publication Date: November 12, 2007
Citation: Shoemaker, C.A., Klesius, P.H., Lim, C.E. 2007. Immunity in Fish. Pezzato, L.E., Barros, M.M. and Furuya, W.M., Editors. Second Symposium on Nutrition and Health of Fish. November 12-17, 2007. Botucatu-Sao Paulo, Brazil. p. 53-65. Technical Abstract: The fish immune system has evolved with both non-specific (innate immunity) and acquired immune functions (humoral and cell mediated immunity) to eliminate invading foreign living and non-living agents. Fish possess a unique physical barrier (mucus and skin) that acts as the first line of defense against foreign agents. Non-specific humoral molecules in fish include lectins (carbohydrate recognition), lytic enzymes (lysozyme), transferrin (iron binding protein) and complement. Non-specific cells of the fish immune system include monocytes or tissue macrophages, granulocytes (neutrophils) and cytotoxic cells. Macrophages function in phagocytosis and destruction of invading foreign agents, including bacteria. Macrophages are also responsible for antigen processing and presentation in the acquired immune response. Acquired immunity in fish includes both humoral and cell mediated responses. B-cells of fish produce antibody when stimulated. The immunoglobulin (Ig) of fish is restricted to tetrameric IgM and functions in opsonization of bacteria, neutralization of toxins/viruses and is a potent activator of the complement cascade. Intracellular pathogens are controlled by cell-mediated immunity. The cell-mediated response in fish, similar to that in mammals, relies on the presence of accessory cells (macrophages) to present antigen to T-cells. Correct presentation of antigen results in a cascade of events, including cytokine production that regulates the responses. Understanding the fish immune system will enhance our ability to develop vaccines and immunostimulatory molecules that may better direct the immune system to prevent disease in fish.