Exploring Zebrafish Kidney's Role in Blood Formation and Virus Defense

Jenn Hoskins
21st March, 2024

Image Source: Natural Science News, 2024

Key Findings

Zebrafish kidneys act like human bone marrow, producing and activating immune cells
Kidney cells in zebrafish can "remember" viruses, boosting their immune response
Zebrafish kidneys can trigger a full defense, similar to human adaptive immunity

The immune system is a complex defense mechanism that is essential for the survival of all vertebrates, including humans and fish. While we have a relatively good understanding of human immunology, our knowledge of fish immune systems is still expanding. A recent study by researchers at Zhejiang University^[1] has shed new light on this area by examining the role of kidneys in the immune response of zebrafish, a popular model organism in scientific research. Unlike mammals, where the bone marrow is the primary site for blood cell production, fish use their kidneys for this purpose. The study has gone a step further to reveal that the zebrafish kidney is not only a blood cell factory but also a key player in the immune response against viral infections. This discovery is significant because it suggests that the fish kidney is a versatile organ with the dual functionality of a primary lymphoid organ (where immune cells are produced) and a secondary lymphoid organ (where immune cells are activated). The researchers achieved this by creating an atlas of 59 different types of hematopoietic stem/progenitor cells (HSPCs) and immune cells found in the zebrafish kidney. They used a technique called single-cell transcriptome profiling, which allows for the examination of the gene expression of individual cells. This method provided a detailed look at how each cell type responds to a viral infection, revealing a wide range of immune activities. One of the study's key findings was that certain HSPCs in the kidney can develop "trained immunity," which is the ability of innate immune cells to mount a stronger response upon re-exposure to a pathogen. This concept of trained immunity has been previously observed in mammals, but its presence in fish HSPCs highlights the evolutionary conservation of this immune defense strategy. Furthermore, the study found that the zebrafish kidney can generate a complete adaptive immune response, which involves the production of antigen-specific antibodies and immune memory. This is a sophisticated level of immunity typically associated with more complex lymphoid organs like the spleen and lymph nodes in mammals. The Zhejiang University research builds upon earlier studies that have characterized the immune cell populations in other organs of fish. For instance, a comprehensive profiling of tissue-resident macrophages and dendritic cells in adult zebrafish organs was previously conducted^[2]. This study identified various subsets of these cells with specialized functions in immunity and tissue regeneration, providing a foundation for understanding the complexity of the fish immune system. Additionally, research on cartilaginous fishes, such as nurse sharks, has shown that despite the absence of germinal centers, these species can still mount robust antigen-specific responses^[3]. This suggests that the evolutionary roots of complex immune structures like germinal centers may be found in simpler organisms like fish. Another study that contributed to the understanding of fish immunology created an atlas of immune cell types in the zebrafish spleen, revealing the diverse roles these cells play in antiviral immunity^[4]. These findings, along with the new insights from the Zhejiang University study, illustrate that fish immune systems, while distinct, share many functional similarities with those of mammals. The implications of this research are far-reaching. By understanding the immune systems of zebrafish, scientists can gain insights into the evolution of vertebrate immunity. This knowledge could potentially lead to novel strategies for enhancing immune responses in fish, which is valuable for aquaculture and conservation efforts. Furthermore, the parallels between fish and human immune systems may open up new avenues for medical research, including the development of vaccines and immunotherapies. In conclusion, the Zhejiang University study not only expands our knowledge of the fish immune system but also underscores the importance of using model organisms to uncover the fundamental principles of biology that are often conserved across species. The discovery that fish kidneys function as both hematopoietic and immune response sites deepens our understanding of vertebrate immunology and paves the way for future research in the field.

Biotech Genetics Marine Biology

References

Main Study

1) Single-cell RNA sequencing unveils the hidden powers of zebrafish kidney for generating both hematopoiesis and adaptive antiviral immunity.

Published 18th March, 2024

https://doi.org/10.7554/eLife.92424

Related Studies

2) Cross-organ single-cell transcriptome profiling reveals macrophage and dendritic cell heterogeneity in zebrafish.

https://doi.org/10.1016/j.celrep.2023.112793

3) Organized B cell sites in cartilaginous fishes reveal the evolutionary foundation of germinal centers.

https://doi.org/10.1016/j.celrep.2023.112664

4) Single-cell transcriptome profiling reveals diverse immune cell populations and their responses to viral infection in the spleen of zebrafish.

https://doi.org/10.1096/fj.202201505RRRR

Key Findings

References

Main Study

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