Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: April 30, 1999
Publication Date: N/A
Technical Abstract: We have a limited understanding of fish immune mechanisms. A continued effort to understand disease resistance and immunity in commercially important aquaculture species is required. Immunity is the inherited ability to recognize and respond in a defensive way against foreign biotic and abiotic agents. Fish have evolved with both non-specific (innate)and specific immune functions (humoral and cell mediated). Non-specific immune molecules in the serum of fish include the lectins, lytic enzymes, and components of complement. Non-specific immune cells include monocytes, neutrophils and cytotoxic cells. Specific immune cells in fish include B-cells (humoral antibody response) and T-cells (cell mediated response). B-cells, when stimulated, produce an antibody response. The antibody molecule in fish is restricted to tetrameric IgM. A memory response is present which demonstrates that fish have the ability to remember foreign antigen. Specific immunoglobulin in fish functions in opsonization of bacteria, neutralization of virus or toxin and as an activator of complement. Whereas, humoral immunity is important in the defense against extracellular pathogens and toxins, cell mediated immunity is important in the defense against intracellular pathogens. The cell mediated response is similar to that in mammmals and relies on the presence of macrophages to present antigen to the T-cells. Upon stimulation, a cascade of events occurs including production of cytokines that regulate the cell mediated response. Further understanding of the immune mechanisms in fish will aid in development of vaccines that can direct the immune system in an effective manner to prevent disease.