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Published on: September 16, 2018
The ontogeny of MHC class I expression in rainbow trout (Oncorhynchus mykiss)
Uwe Fischer1, Johannes Martinus Dijkstra, Bernd Köllner
1Friedrich-Loeffler-Institutes, Federal Research Centre for Virus Diseases of Animals, D-17493 Greifswald-Insel Riems, Germany. uwe.fischer@rie.bfav.de
Abstract:
In the present study, clonal rainbow trout (Oncorhynchus mykiss) embryos and larvae were assayed for the expression of key molecules involved in specific cell-mediated cytotoxicity using an anti-MHC class I monoclonal Ab and by RT-PCR using specific primers derived from classical MHC class I (class Ia), TCR and CD8. Whereas RT-PCR revealed that MHC class Ia and CD8 were expressed from at least 1 week after fertilisation (p.f.) on, TCR expression was detectable from 2 weeks p.f. Immunohistochemistry indicated an early and distinct expression of MHC class I protein in the thymus. Positive lymphoid, epithelial and endothelial cells were found in the pronephros, in the spleen and in the inner and outer epithelia at later stages. Whereas in older rainbow trout the intestine is counted among the organs of the highest class I expression, during ontogeny it was the last site (39 days after hatching) where such expression was detectable. Knowledge on the appearance of the assayed key molecules during fish development is relevant for the pathogenesis of infections as well as for early vaccine delivery. Besides such information regarding the development of the adaptive immune system, immunohistochemistry revealed that in early larvae MHC class I was expressed in neurons whereas in older rainbow trout this was not observed.
Insights
This study tracked key immune molecules in rainbow trout development. MHC class I and CD8 appeared early, followed by TCR, crucial for adaptive immunity and vaccine strategies.
Area of Science:
- Immunology
- Developmental Biology
- Fish Science
Background:
- Cell-mediated cytotoxicity is vital for adaptive immunity.
- Understanding immune molecule development in fish is crucial for disease management and vaccination.
- Rainbow trout (Oncorhynchus mykiss) serve as a model for fish immunology research.
Purpose of the Study:
- To investigate the developmental expression of key molecules in rainbow trout cell-mediated cytotoxicity.
- To determine the ontogeny of Major Histocompatibility Complex class I (MHC class I), T-cell receptor (TCR), and CD8 expression.
- To correlate immune molecule expression with developmental stages and potential vaccine delivery timing.
Main Methods:
- Reverse transcription polymerase chain reaction (RT-PCR) was used to detect gene expression of MHC class Ia, TCR, and CD8.
- Immunohistochemistry was employed to visualize MHC class I protein distribution.
- Expression patterns were analyzed from early embryonic stages through larval development.
Main Results:
- MHC class Ia and CD8 gene expression was detected from 1 week post-fertilization (p.f.).
- TCR gene expression was detectable from 2 weeks p.f.
- MHC class I protein showed early expression in the thymus, with later detection in lymphoid, epithelial, and endothelial cells in various organs, including the intestine as the last site (39 days post-hatching). Early larvae also showed MHC class I expression in neurons, which diminished in older fish.
Conclusions:
- The study elucidates the developmental timeline of key adaptive immune molecules in rainbow trout.
- Findings provide insights into the ontogeny of cell-mediated cytotoxicity, relevant for understanding fish disease pathogenesis.
- The data supports the potential for strategic early-life vaccination in rainbow trout based on immune system development.
