The impact of Amino Acids on the avian immune system

1. Amino acids are crucial substrates for proteins that mediate all immune functions, including cell and defense proteins. Leukocytes have an excellent ability to compete with other tissues for low levels of some, but not all, of the amino acids. In addition, an immune response is accompanied by the mobilization of nutrients from muscle and other tissues, which supply adequate amounts of some amino acids to the leukocytes, but not all of those needed. In general, developing T lymphocytes appear to be the leukocyte population most susceptible to nutrient deficiencies. With decreased lymphocyte-mediated immunity, exaggerated innate immune system responses often occur during infection and result in robust inflammatory responses and largely explain the accompanying immunopathology.
2. There are a variety of amino acids that modulate the immune system. For example, some of them, as arginine and tryptophan, formulated at dietary inclusion levels that are clearly above the nutritional requirement regulate the type of response to a pathogen. Unlike increasing nutrients from deficient to sufficient levels, where many indices of immunocompetence are elevated, supplementation of immunomodulatory nutrients causes some components of immunity to be elevated and others to be decreased; in other words, the types and intensities of responses are changed.

Conclusions

• The metabolic benefits and costs of the immunoregulatory effects of these nutrients depend on the types of pathogens in the bird’s environment.
• The resulting changes may be favorable for some pathogens and facilitate their damage to the host.
• However, they may increase susceptibility to those pathogens controlled by responses that are diminished by their deficiency.