Macronutrient availability and immune cell responses.

Nutritional status and dietary composition profoundly influence immune responses, with carbohydrates, lipids, and proteins, acting as key regulators of immune cell metabolism, activation, and function. This review synthesizes current evidence on how these macronutrients shape the behavior of innate and adaptive immune cells, including monocytes, macrophages, dendritic cells, neutrophils, T cells, and B cells. We discuss how glucose and fructose differentially modulate inflammatory pathways, trained immunity, and antiviral responses; how saturated and polyunsaturated fatty acids affect immune cell signaling and cytokine production; and how amino acid availability influences metabolic reprogramming, polarization, and effector functions. Emerging findings highlight the complex, context-dependent roles of macronutrients in health and disease, revealing their potential as dietary targets in immune-mediated conditions. Understanding these interactions provides a foundation for nutritional strategies aimed at modulating immunity in metabolic, infectious, and inflammatory diseases.