Molecular Characterization of Immunoglobulin M (IgM) and Polymeric Immunoglobulin Receptor (pIgR) and Expression Response to Vibrio harveyi Challenge in Leopard Coral Grouper (Plectropomus leopardus)

Immunoglobulin M (IgM) is the primary antibody in fish, which transported from epithelial cells into external secretion system by polymeric immunoglobulin receptor (pIgR). In this study, full length of IgM and pIgR complementary DNA sequences leopard coral grouper (Plectropomus leopardus) was characterized, their expression levels under Vibrio harveyi infection were studied. cDNA sequence analysis showed that pl-IgM heavy chain contained an open reading frame (ORF) 1797 bp encoding a polypeptide 597 amino acids consisting signal peptide, variable region, 4 constant regions. pl-pIgR (1041 bp) encodes 346 with 2 Ig-like domains (ILDs). The healthy fish mainly intestine spleen indicates relationship between mucosal-associated lymphoid tissue tissue. Messenger RNA (mRNA) profiles significantly increased intestine, head kidney, spleen, liver after V. infection. two ILDs cloned expressed Escherichia coli BL21 (DE3). recombinant protein had antibacterial function against alginolyticus at 200 ng/μl. Our results indicate are involved immune systemic response immunity grouper.