Adaptive Immune Responses in Teleost Fish

Teleost fish represent a diverse group of bony vertebrates distinguished by a fully functional adaptive immune system. Their lymphoid tissues—principally the thymus, head kidney and spleen—support the development and maturation of both B and T lymphocytes. B cells secrete immunoglobulins, mainly IgM and IgT, which neutralise pathogens and contribute to mucosal defence, while T cells express T-cell receptors (TCR) and co-receptors such as CD4 and CD8 to orchestrate cellular responses against intracellular invaders. A hallmark of teleost immunity is the conservation of co-stimulatory requirements and the emergence of cytokine-driven T helper cell subsets. Distinct phenotypes analogous to Th1, Th2 and Th17 cells regulate macrophage activation, antibody production and inflammatory homeostasis. Recent insights have underscored the interplay between antigen presentation, metabolic reprogramming and transcriptional control in shaping immune memory. This evolutionary perspective reveals striking parallels with mammalian systems and highlights teleosts as powerful models for probing fundamental mechanisms of adaptive immunity. Advances in high-throughput sequencing and monoclonal antibody development have enabled detailed profiling of lymphocyte subsets, informing rational vaccine design and disease management strategies in global aquaculture.

Research from Nature Portfolio

Recent studies have developed monoclonal antibodies against two CD4 homologues in flounder, enabling the isolation and characterisation of CD4-1+ and CD4-2+ T lymphocytes. In vitro stimulation with poly I:C, phorbol ester and β-glucan revealed distinct transcription factor and cytokine expression patterns corresponding to Th1, Th2 and Th17 phenotypes. These findings demonstrate that teleost T cell subsets undergo differentiation processes analogous to those in mammals, establishing a framework for dissecting helper T cell biology in fish.

Adaptive Immune Responses in Teleost Fish publication trend

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

Technical terms

CD4+ T lymphocyte: A helper T cell subtype bearing the CD4 co-receptor that coordinates immune responses by releasing cytokines and assisting B cell activation.

Immunoglobulin M (IgM): The primary antibody isotype in teleost fish that mediates early humoral defence against pathogens.

Co-stimulatory signal: A secondary activation cue, often delivered via CD28, required alongside antigen recognition to fully activate T cells.

mTORC1: A multi-protein complex that senses nutrient availability and regulates cell growth, metabolism and immune cell differentiation.

Th1 cell: A subset of helper T cells characterised by interferon-γ production, crucial for defence against intracellular bacteria and viruses.

MAPK/ERK pathway: A conserved signalling cascade that translates extracellular signals into cellular responses, influencing T cell activation and function.

T-cell receptor (TCR): A membrane complex on T cells that recognises antigenic peptides presented by major histocompatibility complex molecules.

References

1. Kinetics of T lymphocyte subsets and B lymphocytes in response to immunostimulants in flounder (Paralichthys olivaceus): implications for CD4+ T lymphocyte differentiation. Scientific Reports (2020).
2. Glutamine Metabolism Underlies the Functional Similarity of T Cells between Nile Tilapia and Tetrapod. Advanced Science (2023).
3. Full T-cell activation and function in teleosts require collaboration of first and co-stimulatory signals. 动物学研究 (2024).
4. IL-2–mTORC1 signaling coordinates the STAT1/T-bet axis to ensure Th1 cell differentiation and anti-bacterial immune response in fish. PLOS Pathogens (2022).