Complement Component 3 (C3) is a crucial protein in the immune system that plays a key role in the complement system, which helps the body fight infections. C3 is involved in opsonization, a process that marks pathogens for destruction by immune cells, and it also helps in the formation of the membrane attack complex, which can directly destroy bacteria and infected cells. When C3 is activated, it can split into two fragments, C3a and C3b. C3a acts as a signaling molecule that attracts immune cells to the site of infection, while C3b enhances the ability of phagocytes to engulf and eliminate pathogens. Proper functioning of C3 is essential for an effective immune response.