Characteristics of the polymeric immunoglobulin receptor (pIgR) of commercial grass carp and the immune response of pIgR and immunoglobulin to Flavobacterium columnare
The transcytosis of polymeric immunoglobulins is primarily regulated by the polymeric immunoglobulin (pIg) receptor (pIgR), which can activate the host immune system and protect against pathogen invasion. To improve understanding of the immune defense of teleost fish, in this study for the first time the full-length complementary DNA (cDNA) sequence of the pIgR in grass carp Ctenopharyngodon idellus was cloned and characterized; its messenger RNA (mRNA) expression and molecular functions were also investigated. We determined that the complete sequence of the pIgR cDNA has 1640 nucleotides, which includes a 1011-base pair (bp) open reading frame, a 68-bp 5′ untranslated region (UTR), and a 561-bp 3′ UTR. Similar to other teleost homologs, the grass carp pIgR gene encodes a 336-amino acid transmembrane protein that contains an extracellular region with two immunoglobulin-like domains, a transmembrane region, and an intracellular region. Reverse transcription-polymerase chain reaction revealed the presence of the pIgR in all tested tissues of grass carp, with the highest levels in skin, gill, intestine, and liver. In addition, the immune response to Flavobacterium columnare of the pIgR and its two ligands (IgM and IgZ) was investigated. The patterns of increase in IgM and IgZ mRNA translation were similar to that of the pIgR. These results should aid the development of novel strategies against fish diseases.
KeywordsFish disease Ctenopharyngodon idellus Mucosal immunity Defense Transcytosis
This study was supported by a key research project of Shandong province (2018GNC110034), the Natural Science Foundation of Shandong, the National Natural Science Foundation of China (grant 31440090), and the Agricultural Seed Project of Shandong province (2014lz042).
Compliance with ethical standards
Conflict of Interest
The authors declare that they have no conflict of interest.
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