Abstract
AbstractSturgeon immunity is relevant for basic evolutionary and applied research, including caviar‐ and meat‐producing aquaculture, protection of wild sturgeons and their re‐introduction through conservation aquaculture. Starting from a comprehensive overview of immune organs, we discuss pathways of innate and adaptive immune systems in a vertebrate phylogenetic and genomic context. The thymus as a key organ of adaptive immunity in sturgeons requires future molecular studies. Likewise, data on immune functions of sturgeon‐specific pericardial and meningeal tissues are largely missing. Integrating immunological and endocrine functions, the sturgeon head kidney resembles that of teleosts. Recently identified pattern recognition receptors in sturgeon require research on downstream regulation. We review first acipenseriform data on Toll‐like receptors (TLRs), type I transmembrane glycoproteins expressed in membranes and endosomes, initiating inflammation and host defence by molecular pattern‐induced activation. Retinoic acid‐inducible gene‐I‐like (RIG‐like) receptors of sturgeons present RNA and key sensors of virus infections in most cell types. Sturgeons and teleosts share major components of the adaptive immune system, including B cells, immunoglobulins, major histocompatibility complex and the adaptive cellular response by T cells. The ontogeny of the sturgeon innate and onset of adaptive immune genes in different organs remain understudied. In a genomics perspective, our new data on 100 key immune genes exemplify a multitude of evolutionary trajectories after the sturgeon‐specific genome duplication, where some single‐copy genes contrast with many duplications, allowing tissue specialization, sub‐functionalization or both. Our preliminary conclusion should be tested by future evolutionary bioinformatics, involving all >1000 immunity genes. This knowledge update about the acipenseriform immune system identifies several important research gaps and presents a basis for future applications.
Highlights
Research on sturgeon immunity is highly relevant for basic evolutionary and applied research, including caviar- and meat-producing aquaculture, protection of wild sturgeons and their re-introduction through conservation aquaculture
All immune effector cells differentiate in haematopoietic tissues from haematopoietic stem cells into myeloid and lymphoid lineages, except T cells that only develop in the thymus (Boehm et al 2012a; Boehm & Swann 2014)
In the gut of sturgeon, mucosa-associated lymphoid tissue (MALT) has been observed (F€ange 1986; Lange et al 2000), but studies on its presence in other organs are scarce in Acipenseriformes
Summary
Research on sturgeon immunity is highly relevant for basic evolutionary and applied research, including caviar- and meat-producing aquaculture, protection of wild sturgeons and their re-introduction through conservation aquaculture. In the evolutionary arms race between hosts and pathogens, vertebrates evolved a complex immunity, a decentralized system, composed of a variety of humoral and cellular components (Murphy & Weaver 2016). The immune response is conceptually categorized into and realized via the interrelated mechanisms of the innate and the adaptive immune system (Yuan et al 2014; Iwasaki & Medzhitov 2015). Both immune systems are thought to co-evolve in vertebrates, a paradigm recently challenged by Swann et al (2020) in anglerfish, where co-evolution of innate and adaptive immunity has been disentangled
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