ABSTRACT

The immune system is a remarkably adaptive defense system that has evolved in vertebrates to protect them from invading pathogenic microorganisms. It is able to generate an enormous variety of cells and molecules capable of specifically recognizing and eliminating an apparently limitless variety of foreign invaders. These cells and molecules act together in an adaptable dynamic network to protect the host (Kuby, 1994).

Overview

Immunity is the ability to resist infection. Immunity can be classified into two components: nonspecific and specific. Innate or nonspecific immunity refers to the basic resistance to disease that a species possesses. Innate immunity can be described as comprising four types of defensive barriers: 1) anatomic (skin), 2) physiologic (temperature, pH, oxygen tension), 3) phagocytic (ingestion of macromolecules by macrophages and neutrophils), and 4) inflammatory (vasodilatation and capillary permeability). Acquired or specific immunity is immunity induced by exposure to an antigen, naturally or via vaccination). Acquired or specific immunity can be further divided into two subcategories: humoral and cell mediated immunity. The humoral branch of the immune system involves the interaction of B cells with extracellular antigen and their subsequent proliferation and differentiation into antibody-secreting cells that are specific for a certain antigen. Antibodies secreted by B cells function as the effector of the immune humoral response by binding to an extracellular antigen and neutralizing and/or facilitating its elimination. Cell-mediated immunity involves the interaction of T cells and their associated cytokines to eliminate intracellular pathogens (Galyean et al., 1999).

Functionally, an immune response can be divided into two interrelated activities; recognition and response. The immune system is able to recognize subtle chemical differences that distinguish one foreign pathogen from another (Kuby, 1994). At the same time, the system is able to discriminate between foreign molecules and the body’s own cells and proteins. Once a foreign protein is recognized, the immune system enlists the participation of a variety of cells and molecules to mount an appropriate response known as the effector response, which is uniquely suited to eliminate a specific type of pathogen. Later exposure to the same foreign organism induces a memory response, characterized by a heightened immune response that serves to eliminate the pathogen and prevent disease. Overall, the basic function of the immune system in eukaroytes is to recognize self from non-self and thus prevent disease.

Nutritional immunology, or immunonutrition is a scientific subdiscipline interrelating the fields of nutrition and immunology. Although these disciplines seem quite different, numerous experiments have shown that animals must be supplied with a diet that is palatable and non-toxic and which contains the required nutrients, in adequate amounts, proper proportions, and available forms for optimal immune function. This presentation in intended to review the interrelationships of nutrients and the immune system relative to animal production as well as discuss certain factors that may inhibit nutrient availability to the animal.