Mucosal Immunity Mechanisms in Teleost Fish

Teleost fish deploy a sophisticated mucosal immune system at their body surfaces—including gut, gills, skin and nasal passages—that balances defence against pathogens with tolerance of commensal microbiota. Each mucosal surface is guarded by diffuse mucosa-associated lymphoid tissues (MALTs) hosting specialised B and T lymphocytes adapted to the aquatic environment. Among the three teleost immunoglobulin isotypes, IgT has emerged as the principal mucosal antibody, orchestrating pathogen neutralisation and microbiota homeostasis in a manner analogous to mammalian IgA. Polymeric IgM also contributes to mucosal protection, and teleost IgD may aid in antigen recognition at epithelial interfaces. Innate barriers—including mucus secretions rich in antimicrobial peptides and lectins—act in concert with cellular components such as phagocytes and dendritic-like cells to mount rapid responses. Epithelial cells actively sample antigens and secrete chemokines that recruit lymphocytes to the mucosa, while the resident microbiome educates immune development. Insights into mucosal immunity in teleosts have profound implications for aquaculture, guiding the rational design of immersion and oral vaccines to enhance disease resistance in farmed species.

Research from Nature Portfolio

Recent studies have elucidated the molecular architecture of teleost mucosal antibodies and their ancient origins. Cryo-electron microscopy has revealed that teleost IgM assembles as a tetrameric polymer lacking a joining chain, with eight C-terminal tailpieces forming a β-sandwich-like domain that stabilises inter-Fc interactions. This unique assembly diversifies effector functions and underpins mucosal secretion. Complementing these structural insights, work on respiratory mucosa demonstrates that IgT+ B cells proliferate locally within the gill mucosa upon pathogen exposure, generating pathogen-specific IgT. Moreover, gill microbiota are heavily coated with IgT, providing direct evidence that specialised mucosal immunoglobulins function at aquatic respiratory surfaces—a feature predating the emergence of tetrapods and highlighting an ancient evolutionary link between mucosal barriers and adaptive immunity.

Mucosal Immunity Mechanisms in Teleost Fish publication trend

The graph below shows the total number of articles in mucosal immunity mechanisms in teleost fish across all publications each year (not limited to Nature Index journals).

Technical terms

MALT: Mucosa-associated lymphoid tissue, diffuse aggregates of immune cells in mucosal surfaces that initiate local adaptive responses. IgT: Teleost-specific immunoglobulin isotype specialised for mucosal defence, functionally analogous to mammalian IgA. IgM: Predominant systemic immunoglobulin in teleosts, forming polymeric assemblies that also contribute to mucosal protection. Cryo-electron microscopy: Imaging technique that freezes specimens for high-resolution structural analysis of macromolecular complexes. β-sandwich-like domain: Structural motif comprising two β-sheets packed together, observed in teleost IgM tailpiece assemblies. HSP70-JNK signalling: Stress-responsive molecular pathway involving heat shock protein 70 and c-Jun N-terminal kinase, critical for mucosal immune activation in skin.

References

1. The structure of the teleost Immunoglobulin M core provides insights on polymeric antibody evolution, assembly, and function. Nature Communications (2023).
2. Mucosal immunoglobulins at respiratory surfaces mark an ancient association that predates the emergence of tetrapods. Nature Communications (2016).
3. Ocular mucosal homeostasis of teleost fish provides insight into the coevolution between microbiome and mucosal immunity. Microbiome (2024).
4. Identification and characterization of immunoglobulin tau (IgT) in Asian Seabass (Lates calcarifer) and mucosal immune response to nervous necrosis virus. Frontiers in Immunology (2023).
5. Skin as outermost immune organ of vertebrates that elicits robust early immune responses after immunization with glycoprotein of spring viraemia of carp virus. PLOS Pathogens (2024).