B Cell Immunology in Teleost Fish

Teleost fish represent the earliest vertebrates possessing an adaptive immune system underpinned by B lymphocytes. In these species, B cells develop primarily within the anterior kidney and spleen and differentiate into distinct lineages expressing immunoglobulin M (IgM) or the mucosal isotype IgT. Unlike mammals, teleosts lack lymph nodes and germinal centres, yet they mount robust humoral responses through specialised plasma cells and long-lived memory B cells. Teleost B cells also display innate-like functions, notably phagocytosis and cytokine production, bridging innate and adaptive immunity. Advances in omics technologies have revealed extensive cellular heterogeneity, unconventional antigen-presenting capacities and evolutionary parallels with mammalian B1-B cells. This body of research not only deepens our understanding of vertebrate immunology but also informs vaccine design and disease management in aquaculture, with implications for global food security and ecosystem health.

Research from Nature Portfolio

Studies have demonstrated that interleukin-6 acts as a potent differentiation factor for trout IgM+ B cells in the absence of germinal centres, driving proliferation, NF-κB activation, Blimp1 upregulation and enhanced IgM secretion, while bacterial lipopolysaccharide induces a hybrid activated state combining antibody production with antigen-presenting functions. Parallel work on Atlantic salmon has uncovered that CpG motifs engage TLR9 and TLR21 on IgM+ B cells, boosting secretion of IgM, upregulating MHC II and the co-stimulatory molecules CD83 and CD40, and triggering a type I interferon response. These findings highlight direct innate receptor-mediated modulation of teleost B cell functionality and differentiation pathways.

B Cell Immunology in Teleost Fish publication trend

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

Technical terms

Teleost: A diverse infraclass of bony fishes that possess adaptive immune systems including specialised B cells.

IgM+ B cell: B lymphocyte expressing surface immunoglobulin M, central to primary antibody responses.

IgT: A teleost-specific immunoglobulin isotype predominantly involved in mucosal immunity.

Memory B cell: Long-lived lymphocyte retaining antigen experience for rapid secondary responses.

Plasma cell: Differentiated B cell dedicated to high-rate antibody secretion during humoral immunity.

Phagocytic B cell: B lymphocyte capable of engulfing particulate antigens and presenting processed peptides.

Single-cell RNA sequencing (scRNA-seq): Technique to profile gene expression of individual cells for high-resolution cell-type mapping.

Toll-like receptor (TLR): Innate immune receptor recognising conserved microbial patterns to initiate immune activation.

MHC II: Major histocompatibility complex class II molecule presenting antigenic peptides to CD4+ T cells.

References

1. Immunological memory in a teleost fish: common carp IgM+ B cells differentiate into memory and plasma cells. Frontiers in Immunology (2024).
2. Mapping the cellular landscape of Atlantic salmon head kidney by single cell and single nucleus transcriptomics. Fish & Shellfish Immunology (2024).
3. Fish Lymphocytes: An Evolutionary Equivalent of Mammalian Innate-Like Lymphocytes?. Frontiers in Immunology (2018).
4. Recent Advances on Phagocytic B Cells in Teleost Fish. Frontiers in Immunology (2020).
5. Distinct Differentiation Programs Triggered by IL-6 and LPS in Teleost IgM+ B Cells in The Absence of Germinal Centers. Scientific Reports (2016).
6. Profiling Atlantic salmon B cell populations: CpG-mediated TLR-ligation enhances IgM secretion and modulates immune gene expression. Scientific Reports (2018).