Amino acids are fundamental to sustaining life. They are crucial for intracellular processes, such as energy metabolism, biosynthesis of nucleotides, and maintenance of oxidative homeostasis. These processes ensure the proper functioning of cells (including immune cells) and organs. Many studies have demonstrated that immune cells, as key players in immune regulation, have distinct amino acid demands, and their rapid growth and activation are shaped by amino acid availability in their microenvironment. In particular, the proliferation, maturation, and functional responses of innate immune cells are closely linked to amino acid metabolism. The transport, sensing, and mobilization of amino acids drive metabolic reprogramming to support these processes. Therefore, this review focuses on the influence of amino acids on the fate and function of immune cells across development, homeostasis, activation, and effector phases, highlighting the underlying mechanisms. It provides a scientific basis for improving disease resistance and production efficiency in animals.
