Temporal dynamics of innate immune gene expression in teleost fish: A phase-based framework from inflammatory activation to regulatory homeostasis.

Teleost fish are continuously exposed to biological pressures and environmental changes that require dynamic and coordinated regulation of innate immunity. In aquaculture research, molecular biomarkers based on immune gene expression are increasingly used to evaluate responses to diverse biological interventions and environmental challenges. However, changes in immune gene expression are still frequently interpreted in a linear manner as indicators of increased or decreased immune capacity, without adequate consideration of temporal dynamics, response phases, and the underlying biological context. This review presents a conceptual synthesis of innate immune modulation in teleost fish by integrating bibliometric mapping with biological interpretation of immune gene regulation, with emphasis on the coordination between early inflammatory activation, regulatory transition, and resolution of the immune response, as well as their relationship with relatively conserved signal transduction pathways, particularly the Toll-like receptor (TLR)-MyD88-NF-κB axis. The synthesis indicates that innate immune gene expression is more appropriately understood as an indicator of the direction and coordination of immune responses rather than as a single measure of immune system strength. The induction of IL-1β, TNF-α, IL-8, and NF-κB reflects inflammatory activation that depends on biological context and observation time, whereas IL-10, TGF-β, and other regulatory mediators reflect mechanisms involved in inflammatory control and the restoration of homeostasis. This review offers a mechanism-based interpretative framework for understanding the dynamics of innate immune biomarkers in teleost fish and supports the development of more context-sensitive approaches to fish health evaluation in modern aquaculture systems.