Complement C3 Regulates Inflammatory Response and Monocyte/Macrophage Phagocytosis of Streptococcus agalactiae in a Teleost Fish

• Published in: International journal of molecular sciences Vol. 23; no. 24; p. 15586
• Main Authors: Bai, Hao, Mu, Liangliang, Qiu, Li, Chen, Nuo, Li, Jiadong, Zeng, Qingliang, Yin, Xiaoxue, Ye, Jianmin
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 09-12-2022; MDPI
• Subjects: Amino acid sequence; Animals; Aquaculture; Bacteria; Bacterial infections; Cichlids - genetics; Complement; complement 3 (C3); Complement activation; Complement C3 - genetics; Complement C3 - metabolism; Complement component C3; Cytokines; Fish Diseases; Fish Proteins - metabolism; Gene expression; Gene Expression Regulation; Immune system; Immunity, Innate - genetics; Immunomodulation; Infections; Inflammation; Inflammatory response; Innate immunity; Lectins; Liver; Macrophages; Macrophages - metabolism; Monocytes; Monocytes - metabolism; mRNA; Muscles; Oreochromis niloticus; Pathogens; Phagocytosis; Proteins; Recombinant Proteins - metabolism; Spleen; Streptococcal Infections - veterinary; Streptococcus agalactiae; Streptococcus infections; Tilapia; inflammatory response; phagocytosis; Oreochromis niloticus; Streptococcus agalactiae; complement 3 (C3)
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms232415586

The complement system is composed of a complex protein network and is pivotal to innate immunity. Complement 3 (C3) is a critical protein in the complement cascade and participates in complement activation and immune defense. In this study, C3 from Nile tilapia (
) was cloned and its function in resisting pathogen infection was characterized. The full length of OnC3 open reading frame is 4974 bp, encoding 1657 aa, and the predicted protein mass weight is 185.93 kDa. The OnC3 amino acid sequence contains macroglobulin domains. The expression pattern of OnC3 mRNA in the tissues of healthy fish was detected, with the highest in the liver and the lowest in the muscle. After challenged with
and
, the expression of OnC3 mRNA was significantly up-regulated in the liver, spleen, and head kidney. Further, the recombinant OnC3 protein alleviated the inflammatory response and pathological damage of tissues after infected with
. Moreover, the OnC3 promoted the phagocytosis of monocytes/macrophages to
. The data obtained in this study provide a theoretical reference for in-depth understanding of C3 in host defense against bacterial infection and the immunomodulatory roles in teleost fish.