An immunoglobulin superfamily member (CgIgIT2) functions as immune inhibitory receptor to inhibit the inflammatory cytokine expressions in Crassostrea gigas. (July 2023)

• Record Type: Journal Article
• Authors: Yan, Xiaoxue; Sun, Jiejie; Yang, Wenwen; Li, Xiaopeng; Yang, Qian; Li, Yinan; Wu, Wei; Wei, Ping; Wang, Lingling; Song, Linsheng
• Is Part Of: Developmental and comparative immunology. Volume 144(2023)
• Publication Date: 2023-07
• Subjects: Immune inhibitory receptor -- Microbes -- Inflammatory cytokine -- Vibrio splendidus -- Crassostrea gigas; Immunology -- Periodicals; Developmental immunology -- Periodicals; 616.079
• DOI: 10.1016/j.dci.2023.104708
• Languages: English
• ISSNs: 0145-305X

Abstract

Abstract: Immune inhibitory receptors are increasingly acknowledged as potent regulators of immune response, which inhibit the overactivation of immune system and play an important role in maintaining immune homeostasis. In the present study, a novel immunoglobulin superfamily member ( Cg IgIT2) was identified from the Pacific oyster, Crassostrea gigas . The protein sequence of Cg IgIT2 contained one signal peptide, four Ig domains, one fibronectin type III domain, one transmembrane domain, and a cytoplasmic tail with two intracellular immunoreceptor tyrosine-based inhibitory motifs (ITIMs) and one immunoreceptor tyrosine-based switch motif (ITSM). The mRNA transcripts of Cg IgIT2 were widely expressed in all the tested tissues, including haemolymph, gill, mantle, adductor muscle, labial palp, gonad and hepatopancreas, with the highest expression in haemolymph. The mRNA expressions of Cg IgIT2 in haemocytes increased significantly at 24, 48 and 72 h after Vibrio splendidus stimulation. The positive green signals of Cg IgIT2 protein were mainly detected in granulocytes of haemocytes, which were 1.27-fold and 2.15-fold ( p < 0.05) higher than that of semi-granulocytes and agranulocytes, respectively. And Cg IgIT2 was mainly located in the membrane and cytoplasm of haemocytes. The recombinant protein of Cg IgIT2-4 × Ig (r Cg IgIT2-4 × Ig) exhibited binding activity towards multiple pathogen-associated molecular patterns (PAMPs), including lipopolysaccharides (LPS), peptidoglycan (PGN), mannose (MAN) and polyinosinic-polycytidylic acid (Poly (I: C)) with the highest affinity for LPS. r Cg IgIT2-4 × Ig could also bind Gram-negative bacteria ( V. splendidus, V. anguillarum, Escherichia coli ), Gram-positive bacteria ( Staphylococcus aureus, Bacillus subtilis ), and fungi ( Pichia pastoris ). In the blocking assay with anti- Cg IgIT2 antibody, the mRNA expressions of interleukins ( Cg IL17-1, Cg IL17-3 and Cg IL17-6) and tumor necrosis factors ( Cg TNF-1 and Cg TNF-2) in haemocytes all increased significantly at 12 h after V. splendidus stimulation. These results suggested that Cg IgIT2 could function as an inhibitor receptor to bind different PAMPs and microbes, as well as inhibit the mRNA expressions of multiple inflammatory cytokines in oysters. Highlights: The mRNA expression of Cg IgIT2 increased significantly after V. splendidus stimulation. Cg IgIT2 displayed the binding activity to various PAMPs and microbes. Cg IgIT2 inhibited the mRNA expressions of inflammatory cytokines after V. splendidus stimulation .