Identification, molecular characterization and functional analysis of interleukin (IL)-2 and IL-2like (IL-2L) cytokines in sea bass (Dicentrarchus labrax L.)

Francesco Buonocore* (Corresponding Author), Marco Gerdol, Alberto Pallavicini, Valentina Stocchi, Elisa Randelli, Maria Cristina Belardinelli, Andrea Miccoli, Paolo Roberto Saraceni, Christopher J. Secombes, Giuseppe Scapigliati, Tiehui Wang

*Corresponding author for this work

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In mammals, interleukin (IL)-2, initially known as a T-cell grow factor, is an
immunomodulatory cytokine involved in the proliferation of T cells upon antigen activation. In bony fish, some IL-2 orthologs have been identified, but, recently, an additional IL-2like (IL-2L) gene has been found. In this paper, we report the presence of these two divergent IL48 2 isoforms in sea bass (Dicentrarchus labrax L.). Genomic analyses revealed that they originated from a gene duplication event, as happened in most percomorphs. These two IL-2 paralogs show differences in the amino acid sequence and in the exon 4 size, and these features could be an indication that they bind preferentially to different specific IL-2 receptors. Sea bass IL-2 paralogs are highly expressed in gut and spleen, which are tissues and organs involved in fish T cell immune functions, and the two cytokines could be up regulated by both PHA stimulation and vaccination with a bacterial vaccine, with IL-2L being more inducible. To investigate the functional activities of sea bass IL-2 and IL-2L we produced the corresponding recombinant molecules in E. coli and used them to in vitro stimulate HK and spleen leukocytes. IL-2L is able to up-regulate the expression of markers related to different T cell subsets (Th1, Th2 and Th17) and to Treg cells in HK, whereas it has little effect in spleen. IL-2 is not active on these markers in HK, but shows an effect on Th1 markers in spleen. Finally, the stimulation with recombinant IL-2 and IL-2L is also able to induce in vitro proliferation of HK- and spleen-derived leukocytes. In conclusion, we have demonstrated that sea bass possess two IL-2 paralogs that likely have an important role in regulating T cell development in this species and that show distinct bioactivities.
Original languageEnglish
Article number154898
Number of pages13
Early online date6 Nov 2019
Publication statusPublished - Feb 2020

Bibliographical note

This research was supported by the European Commission under the 7th Framework Programme for Research and Technological Development (FP7) of the European Union (Grant Agreement 311993 TARGETFISH) and by the “Department of Excellence-2018” Program (Dipartimenti di Eccellenza) of the Italian Ministry of Education, University and Research, DIBAF-Department of University of Tuscia, Project “Landscape 4.0 – food, wellbeing and environment”.


  • interleukin-2
  • sea bass
  • expression
  • bioactivity
  • T cell development
  • Interleukin-2
  • Expression
  • Bioactivity
  • Sea bass


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