Diversity and specificity of the teleost immune system - A transcriptome study on two fish species

• Main Author: Haase, David
• Format: Thesis
• Language: English
• Published: 2013
• Subjects: atlantic cod
• Online Access: https://oceanrep.geomar.de/id/eprint/22102/; https://oceanrep.geomar.de/id/eprint/22102/1/Diss.%202013%20Haase,D.pdf

All living organisms are constantly surrounded by detrimental pathogens. Protection against those pathogens is realized by the immune system. In vertebrates, the immune system is classically divided into fast responding, unspecific innate immunity and slow-going, highly specific adaptive immunity, including immune memory. Until recently, our understanding of immune responses in vertebrates relied on the assumption that jawed vertebrates share common immune mechanisms and that adaptive immunity is a unique feature of this taxon. However, more recent studies have shown that invertebrates also possess specific immune responses and immune memory. Among extant vertebrates, fish are the most basal class of organisms which possess all elements of vertebrate immunity. As poikilothermic organisms, their adaptive immune response, in contrast to innate immunity, is strongly influenced by the surrounding temperature. This elevates the importance of innate immune mechanisms in fish and highlights their unique role in the evolution of the vertebrate immune system. In this work I used high-throughput sequencing of mRNA (RNA-seq) to investigate the transcriptome of two teleost fish species and to shed light on the diversity of vertebrate immunity. In my first project I examined the transcriptome of an emerging model species, the broad-nosed pipefish (Syngnathus typhle). The genus Syngnathus exhibits male pregnancy and recent studies have shown that male pipefish contribute to the immunization of their offspring. Here I found that, next to atlantic cod, pipefish is the second vertebrate species lacking genes of the MHC class II complex, a central part of adaptive immune memory. Due to a different set of absent genes compared to cod, the loss of MHC II has likely been independent, emphasizing the importance of evolutionary processes to shape immune system components in vertebrates. Next to pipefish I worked on gene expression patterns of three-spined sticklebacks (Gasterosteus aculeatus), an important model organism in ecology ...