Thymus development in the zebrafish (Danio rerio) from an ecoimmunology perspective. Issue 10 (11th December 2020)

• Record Type: Journal Article
• Authors: Kernen, Larissa; Rieder, Jessica; Duus, Annette; Holbech, Henrik; Segner, Helmut; Bailey, Christyn
• Other Names: Titon Stefanny C. M. guestEditor.; Assis Vania R. guestEditor.
• Is Part Of: Journal of experimental zoology. Volume 333:Issue 10(2020)
• Page Start: 805
• Page End: 819
• Publication Date: 2020-12-11
• Subjects: zebrafish -- thymus -- involution -- ecoimmunology -- tradeoffs -- life history; Zoology -- Periodicals; Zoology; Animal Population Groups -- physiology; Zoology; Electronic journals; Periodical; Periodicals; 590
• DOI: 10.1002/jez.2435
• Languages: English
• ISSNs: 2471-5646

Abstract

Abstract: The thymus is present in all gnathostome vertebrates and is an essential organ for the adaptive immune system via the generation of functional mature T‐cells. Over the life span of mammals, the thymus undergoes morphological and functional alterations, including an age‐related involution, which in humans starts in early life. Life history tradeoffs have been suggested as possible reasons for thymus involution. While in teleost fish, only a few studies have investigated alterations of thymus structure and function over different life stages, resulting in a fragmented database. Here, we investigated the thymus growth of zebrafish ( Danio rerio ) from early life, throughout puberty and reproductive stage, up to 1‐year‐old. We assessed thymus growth by histological and morphometric analyses and thymocyte numbers. Thymus function was assessed by measuring the transcripts of the thymocyte marker genes, ikaros, tcrα, and tcrδ . Additionally, we analyzed gonad maturity and tail homogenate vitellogenin concentrations to align thymus status with the status of the reproductive system. Our results showed that the zebrafish thymus, in contrast to the human thymus, grew strongly during early life and puberty but started to undergo involution when the fish reached the reproductive age. The involution was characterized by reduced thymus area and thymocyte number, altered histoarchitecture, and decreasing thymocyte marker gene transcript levels. Our findings suggest that age‐related changes of the zebrafish thymus do exist and could be partly explained in terms of resource tradeoffs, but also in terms of the ontogenetically late development of a functional adaptive immune system in teleosts. Abstract : Comparison of thymus development between human and zebrafish at key life stages. Research Highlights: Zebrafish thymus growth peaks at puberty and age‐related involution starts at reproduction, in contrast to mammals where thymus involution starts in early life, suggesting different ecological and evolutionary pressures on thymus development.