Intestinal Immune Function in Aquatic Organisms

The intestinal tract of aquatic organisms represents a critical interface between the external environment and the internal milieu, combining physical, chemical and cellular defences to maintain health and resilience. Mucosal surfaces are lined by epithelial cells and mucus layers that house gut‐associated lymphoid tissue, where innate immune cells such as macrophages and dendritic cells collaborate with specialised epithelial cells to detect and neutralise pathogens. Secreted factors including antimicrobial peptides, immunoglobulins and complement proteins form a dynamic humoral defence that prevents infiltration by bacteria, viruses and parasites. Underpinning this defence are intercellular tight junctions that preserve barrier integrity and prevent translocation of harmful agents. Pattern recognition receptors, such as Toll-like receptors, sense microbial-associated molecular patterns and activate downstream signalling pathways including NF-κB and Nrf2, which orchestrate inflammatory and antioxidant responses. Symbiotic microbial communities further prime immune development and competitive exclusion of pathogens. Nutritional status profoundly influences this system: dietary amino acids, minerals and vitamins modulate signalling cascades, antioxidant capacity and the production of cytokines. Environmental stressors—pollutants, salinity shifts and heavy metals—can disrupt epithelial function and immune signalling, with implications for disease susceptibility. Advancing our understanding of intestinal immunity in fish and other aquatic species is essential for sustainable aquaculture, enabling targeted interventions to bolster disease resistance, reduce antimicrobial use and safeguard global food security.

Research from Nature Portfolio

Recent studies have illuminated the role of dietary minerals in sustaining epithelial integrity and immune competence. Foundational work on grass carp has shown that magnesium deficiency compromises intestinal architecture by downregulating tight junction proteins and antioxidant enzymes, while activating pro-apoptotic and inflammatory pathways. This study demonstrated that optimal dietary magnesium levels support redox homeostasis via Nrf2 signalling and maintain barrier function by preserving expression of claudins, occludins and junctional complexes. These findings underscore the importance of mineral nutrition for gut-associated immune defences in aquaculture species.

Intestinal Immune Function in Aquatic Organisms publication trend

The graph below shows the total number of articles in intestinal immune function in aquatic organisms across all publications each year (not limited to Nature Index journals).

Technical terms

Gut‐associated lymphoid tissue (GALT): a specialised immune tissue within the gut wall that contains lymphocytes and antigen-presenting cells for local immune surveillance.

Tight junctions: protein complexes between epithelial cells that seal the paracellular space and prevent uncontrolled passage of substances.

Toll-like receptors (TLRs): a family of pattern recognition receptors that detect conserved microbial molecules and initiate innate immune signalling.

NF-κB signalling pathway: a central transcription factor cascade that regulates inflammatory gene expression in response to stress or infection.

Nrf2: a transcription factor that governs antioxidant gene expression to protect cells from oxidative damage.

Humoral immunity: the aspect of immunity mediated by soluble factors such as antibodies, complement proteins and antimicrobial peptides.

References

1. Evaluation of Gamma-Aminobutyric Acid (GABA) as a Functional Feed Ingredient on Growth Performance, Immune Enhancement, and Disease Resistance in Olive Flounder (Paralichthys olivaceus) under High Stocking Density. Antioxidants (2024).
2. Effects of dietary tryptophan on the antioxidant capacity and immune response associated with TOR and TLRs/MyD88/NF-κB signaling pathways in northern snakehead, Channa argus (Cantor, 1842). Frontiers in Immunology (2023).
3. Dietary Leucine Improves Fish Intestinal Barrier Function by Increasing Humoral Immunity, Antioxidant Capacity, and Tight Junction. International Journal of Molecular Sciences (2023).
4. Dietary magnesium deficiency impaired intestinal structural integrity in grass carp (Ctenopharyngodon idella). Scientific Reports (2018).