Immune System Development in Teleost Fishes

Teleost fishes exhibit a dynamic maturation of their immune systems, beginning as embryos reliant on maternally derived factors and progressing through larval innate defences to a fully functional adaptive repertoire. Early embryos are protected by complement proteins and yolk-associated antimicrobial agents that act as pattern recognition receptors. As larvae hatch and first feed, innate barriers such as phagocytic cells, antimicrobial peptides and Toll-like receptor signalling become increasingly active. The development of primary and secondary lymphoid organs—the thymus, head kidney and spleen—supports lymphocyte differentiation, enabling recombination of antigen receptors on B and T cells. Major histocompatibility complex class I and II molecules diversify under pathogen pressure, although some lineages, notably Gadiformes, have lost MHC class II and compensated with expanded MHC class I clades. This evolutionary plasticity underpins vaccine design, disease resistance breeding and ecological speciation across the world’s freshwater and marine environments.

Research from Nature Portfolio

Genome-scale analyses across multiple teleost lineages reveal that losses of MHC class II genes coincided with repeated expansions of class I repertoires, suggesting alternative modes of antigen presentation that influence speciation rates. In parallel, developmental transcriptome profiling in rainbow trout has defined a staged transition from reliance on innate inflammatory and antimicrobial programmes in embryos and early larvae to the emergence of interferon-mediated antiviral defences and lymphocyte-driven adaptive responses only after first feeding. These findings establish a molecular timeline linking organogenesis of lymphoid tissues to functional immune competence in teleosts.

Immune System Development in Teleost Fishes publication trend

The graph below shows the total number of articles in immune system development in teleost fishes across all publications each year (not limited to Nature Index journals).

Technical terms

Teleost: A diverse infraclass of ray-finned fishes representing the majority of modern fish species.

Innate immunity: The non-specific, first-line defence mechanism of the immune system including phagocytes, complement and antimicrobial peptides.

Adaptive immunity: The antigen-specific immune response characterised by lymphocyte receptors, immunological memory and class-switched antibodies.

Major histocompatibility complex (MHC): Cell-surface proteins essential for antigen presentation to T cells, comprising class I (endogenous peptides) and class II (exogenous peptides).

Pattern recognition receptor (PRR): A receptor that detects conserved molecular signatures of microbes to initiate innate immune responses.

Endolysosomal compartment: Intracellular vesicles that merge endosome and lysosome functions, crucial for antigen processing and protein sorting.

References

1. Maternal Transfer and Protective Role of the Alternative Complement Components in Zebrafish Danio rerio. PLOS ONE (2009).
2. Phosvitin Plays a Critical Role in the Immunity of Zebrafish Embryos via Acting as a Pattern Recognition Receptor and an Antimicrobial Effector*. Journal of Biological Chemistry (2011).
3. Evolution of the immune system influences speciation rates in teleost fishes. Nature Genetics (2016).
4. Unraveling the Evolution of the Atlantic Cod’s (Gadus morhua L.) Alternative Immune Strategy. PLOS ONE (2013).
5. Aeromonas salmonicida subsp. salmonicida Early Infection and Immune Response of Atlantic Cod (Gadus morhua L.) Primary Macrophages. Frontiers in Immunology (2019).
6. Trematode Diplostomum pseudospathaceum inducing differential immune gene expression in sexual and gynogenetic gibel carp (Carassius gibelio): parasites facilitating the coexistence of two reproductive forms of the invasive species. Frontiers in Immunology (2024).
7. Atlantic cod (Gadus morhua) MHC I localizes to endolysosomal compartments independently of cytosolic sorting signals. Frontiers in Cell and Developmental Biology (2023).