Aging-related autonomic nervous system imbalance and adrenergic regulation of immunity: Implications for inflammaging, autoimmunity, and long COVID.

The autonomic nervous system (ANS) plays a central role in immune homeostasis by integrating sympathetic and parasympathetic signals that regulate inflammation, immune cell trafficking, and tolerance. Aging is associated with a progressive autonomic imbalance characterized by sympathetic overactivation, reduced parasympathetic tone, and impaired β-adrenergic signaling in immune cells, which together contribute to inflammaging and immune dysregulation. In this review, we discuss how aging-related alterations in adrenergic pathways affect immune cell differentiation and cytokine networks, with particular emphasis on β₂-adrenergic control of the Th17/regulatory T cell balance through cAMP-dependent mechanisms interacting with cytokine-driven STAT signaling. Chronic sympathetic stimulation and β-adrenergic desensitization weaken these regulatory constraints, favoring pro-inflammatory immune trajectories and loss of immune tolerance. Finally, we propose Long COVID as a paradigmatic condition in which pre-existing inflammaging and autonomic vulnerability are amplified by viral infection, leading to persistent inflammation, impaired immune regulation, and increased susceptibility to autoimmune manifestations.