CpG-induced secretion of MHCIIbeta and exosomes from salmon (Salmo salar) APCs.
Major histocompatibility complex class II (MHCII) is encoded by polymorphic genes present in vertebrates and expressed predominately in leukocytes. Upon leukocyte differentiation, intracellular MHCII is dynamically redistributed within the cells and it is expressed at maximal levels on mature antigen presenting cells (APCs). In addition, APCs secrete MHCII within endosome-derived vesicles known as exosomes which possess diverse immunomodulatory properties. Genetic and biochemical data have confirmed that piscine leukocytes express the MHCII components as well as costimulatory molecules that are necessary for the function of APCs. However data concerning the biosynthesis and the distribution of the MHCII complex within leukocytes of lower vertebrates is scarce. The presented data demonstrates for the first time that salmon leukocytes secrete vesicles that contain exosomal markers and the abundance of MHCII indicates that these exosomes are released by APCs. The secretion was specifically induced by CpG stimulation in vitro and it was observed only in head kidney leukocytes but not in splenocyte cultures. Flow cytometry revealed that, unlike splenocytes, the majority of the MHCII-positive head kidney leukocytes were Ig-negative and a population of cells expressing high levels of surface MHCII underwent degranulation upon CpG stimulation suggesting that the MHCII-containing exosomes were derived from maturing salmon APCs. Gene expression analyses have further demonstrated that CpG-B, despite its relatively weak proinflammatory activity compared to LPS, induced expression of a larger group of genes involved in regulation of the adaptive immune response.
Iliev
Dimitar B
DB
The Norwegian College of Fishery Science, University of Tromsø, N-9037 Tromsø, Norway.
Jørgensen
Sven Martin
SM
Rode
Marit
M
Krasnov
Aleksei
A
Harneshaug
Ingvill
I
Jørgensen
Jorunn B
JB
D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D000938:Antigen-Presenting Cells / Q000187:drug effects* / Q000276:immunology*; D002478:Cells, Cultured; D015226:Dinucleoside Phosphates / Q000494:pharmacology*; D055354:Exosomes / Q000378:metabolism*; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000187:drug effects; D000949:Histocompatibility Antigens Class II / Q000378:metabolism*; D007150:Immunohistochemistry; D007962:Leukocytes / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D046529:Microscopy, Electron, Transmission; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020317:Salmo salar; D013154:Spleen / Q000166:cytology
D000276:Adjuvants, Immunologic; D015226:Dinucleoside Phosphates; D000949:Histocompatibility Antigens Class II; D008070:Lipopolysaccharides; C015772:CpG dinucleotide