Investigating the role of il-4, il-13 and il-10 cytokines in zebrafish immune responses

Abstract

Mucosal surfaces represent the interface between the body and the external environment and they are key sites where antigens are encountered. Here the balance between inflammatory and regulatory responses is critical for the maintenance of homeostasis. Disruption of homeostasis at mucosal surfaces of the lungs and the intestine leads to development of chronic inflammatory disorders such as asthma, allergies, and inflammatory bowel disease. In mammals, cytokines such as IL-4, IL-13 and IL-10 actively participate in the immune responses governing these disorders. Mice lacking these cytokines have become valuable models to study their function, and develop novel strategies for the treatment of the diseases. The field of fish immunology is in great expansion and considerable progress has been made in recent years. However, there is still the need to understand how specialized immune cells and cytokines function, in particular in mucosal tissues such as the gills and the gut (that appear to resemble some aspects of the mammalian lungs and intestine). Here we used the zebrafish model (Danio rerio) to gain insights into il-4, il-13 and il-10 cytokines and characterize their function in the zebrafish immune system. Zebrafish knock-outs for il-4 and il-13 genes were generated using the CRISPR/Cas9 system and the il-10e46/e46 zebrafish line was acquired from the Sanger Institute (Zebrafish Mutation Project). The expression of important cytokines and innate/adaptive immune cell markers was quantified in larvae, adult gills and gut, and upon immune-challenge in the three mutants. Also, histological examination of the gills and gut was performed, providing insights into the function of the aforementioned cytokines in zebrafish immunity. We found that il-4 may be required for generation of neutrophils, specification of M2 macrophages and CD8+ T cell population in zebrafish, suggesting a degree of conservation with mammalian IL-4. Moreover, il-13 appears to be required for generation of neutrophils and lymphocytes but not for M2 macrophages specification, indicating a divergent function from mammalian IL-13. Finally, il-10 was shown to have an anti-inflammatory function, as is the case for mammalian IL-10, and to be required for CD8+ T cell expansion. Although further work will be required to validate these findings, we propose that the il-4-/-, il-13-/- and il-10-/- zebrafish mutants will be valuable models to further investigate the function of these cytokines in the context of infections or disease.

Date of Award	1 Aug 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Judi Allen (Supervisor) & Adam Hurlstone (Supervisor)