Research Progress on the Fish Complement C3 Gene

Abstract

Complement (C) is a serum protein with immunity-related functions and enzymatic activities. It can induce inflammatory responses and antibody formation following activation by substances such as pathogens. Moreover, it is a crucial molecule in the congenital immune defense system. Complement manifests earlier than immunoglobulin in the evolutionary process of fish's immune system. Therefore, the complement system of fish is vital for congenital and acquired immunities. A complement system is a polymolecule system comprising more than 30 soluble proteins, membrane-bound proteins, and complement receptors. It can be activated through three pathways for immunoregulation, the clearance of the immune complex, etc. The liver primarily produces the fish complement C3, which is a significant component of the complement system of fishes. C3 is the hub of three activation pathways. Research works concerning the structure, generation process, expression, and functions of C3 in fishes are reviewed in this study.