Pathogens are able to protect themselves from complement activation. Pathogens have developed different strategies to inhibit complement activation. They can be classified in four different groups. Several pathogens are able to bind regulators of complement activation (RCA), such as FH and C4BP, to decrease C3 deposition. RCA-like expression allows pathogens to block complement activation without the need to recruit complement regulator. Synthesis of proteases specifically against complement proteins degrades complement components. The last group is pathogens able to express C3 convertase inhibitors. Complement System Part II: Role in Immunity. Merle NS, Noe R, Halbwachs-Mecarelli L, Fremeaux-Bacchi V, Roumenina LT - Frontiers in immunology (2015). Not Altered. CC.