Differential Modulation of igT and igM upon Parasitic, Bacterial, Viral, and Dietary challenges in a Perciform Fish. Front. Immunol. 7:637. doi: 10.3389/fimmu.2016.00637
The current study is the first to describe the full sequences of the soluble and membrane-bound forms of Gilthead sea bream IgM and IgT and shows for the first time in a fish model their differential expression in different tissues, upon challenge with different pathogens and infection routes.
Three different immunoglobulin (Ig) isotypes can be found in teleost fish, IgM, IgD, and the teleost-specific IgT. It is widely accepted that IgM expression is dominant in absolute terms in all organs and is essential for immune protection against different pathogens upon different routes of infection. IgT, despite being generally less abundant than IgM in number of transcripts and cells, is undeniably crucial in mucosal immune responses, but its role in systemic responses and the role of IgM in mucosal responses should not be discarded. Gilthead sea bream (Sparus aurata) is a marine species belonging to the Sparidae family (Teleostei: Perciformes). It is the main farmed fish species in the Mediterranean basin, representing an important resource for this area. Several diseases hamper their production, and therefore, any advancement in the knowledge of its immune response will help to combat diseases.
This study found that
--> constitutive expression of sIgM was the highest overall in all tissues, whereas mIgT expression was highest in mucosal tissues, such as gills and intestine.
--> IgM and IgT were differentially regulated upon infection.
--> plant-based diets inhibit IgT upregulation upon intestinal parasitic challenge, which was related to a worse disease outcome.
The authors corroborate the importance of IgT in mucosal responses in a fish species very different to the ones used in most previous IgT studies (salmonids and cyprinids). The current results clearly show that the dynamics of expression of IgM and IgT are very different and depend on the types of pathogen or stimulation, immunization, challenge (intramuscular, anal, bath), tissues, and time after challenge. Finally, the authors propose the fish–E. leei infections and the different dietary interventions as models to further study and unravel the insights of the different Ig isotype functions in teleost fish.
INFOBOX: An antibody, also known as an immunoglobulin (Ig), is a large, Y-shaped protein produced mainly by plasma cells that is used by the immune system to neutralize pathogens such as bacteria and viruses. The antibody recognizes a unique molecule of the harmful agent, called an antigen.