Anatomy of the Immune System. Cells and Tissues of the Immune System of Fish. The Immune System: Nonspecific Defense Mechanisms. Cellular Defenses. Humoral Defense. Specific Defense Mechanisms. Cellular Defenses. Humoral Defenses. Immunomodulation. Natural Changes in the Immune System of Fish. Environmental Factors in Fish Health, Immunological Aspects. Endogenous Factors. Infection and Disease. Bacterial, Viral, And Parasitic. Subject Index.