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

Abstract

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 (Oreochromis niloticus) 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 Streptococcus agalactiae and Aeromonas hydrophila, 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 S. agalactiae. Moreover, the OnC3 promoted the phagocytosis of monocytes/macrophages to S. agalactiae. 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.

Transcriptome Analysis Revealed Potential Immune-Related Genes of Head Kidney in the Yellow Catfish (Pelteobagrus fulvidraco) Challenged with Aeromonas hydrophila

“…C3 complement component (C3) plays a critical role in the complement cascade and immune defense by participating in complement activation [53]. The mRNA expression levels of C3 in Oreochromis niloticus were significantly upregulated in the liver, spleen, and head kidney after challenge with Streptococcus agalactiae and A. hydrophila [54]. Similarly, Ctenopharyngodon idella showed significantly upregulated C3 mRNA expression levels in the gill, liver, spleen, intestine, trunk kidney, and head kidney after infection with A. hydrophila [55].…”

Aging hallmarks of the primate ovary revealed by spatiotemporal transcriptomics

“…6D ). The top 10 overlapped genes included SERPINA3 , C3 , COL6A2 , LTBP4 , MGP , APOE , MT2 , ITGA5 , THBS1 , and IGFBP4 , most of which are associated with inflammatory response and fibrosis ( Bai et al, 2022 ; Isola et al, 2023 ; Lin et al, 2022 ) ( Fig. 6E ).…”

Effects on growth performance and immunity of Monopterus albus after high temperature stress

“…Further research shows that high temperature stimulation can promote heat shock response, apoptosis, and the expression of immune defense-related genes ( Jeyachandran et al, 2023 ) which is especially obvious in the classical activation of the complement system ( Beemelmanns et al, 2021 ). As a key part of teleosts’ natural defenses, the classical complement system can kill pathogens that get inside through LZM ( Bai et al, 2022 ). In addition, stimulation at high temperatures can also trigger the inflammatory reaction of animals at variable temperatures, which is a key mechanism to deal with virus infection ( Sanhueza et al, 2021 ).…”