Complement System

Complement system proteins are a group of plasma and membrane-associated proteins that play essential roles in innate immunity and immune regulation. The complement system can be activated through the classical, lectin, or alternative pathways, leading to pathogen recognition, inflammation, opsonization, and cell lysis. Complement proteins typically function through sequential proteolytic activation and protein–protein interactions. Key components include complement factors, complement receptors, regulatory proteins, and terminal pathway proteins. These proteins are widely used in studies of host defense, inflammatory diseases, autoimmune disorders, infection, and therapeutic antibody mechanisms.