Abstract: The complement system is part of the innate immune system and is highly regulated by regulatory proteins belonging to the Regulators of Complement Activation (RCA) family. It is known that lack of regulation causes damage to host cells and deficiencies in the regulation is also linked to diseases such as age-related macular degeneration, atypical hemolytic uremic syndrome, and dense deposit disease. The regulatory proteins primarily include decay-accelerating factor (DAF; CD55), membrane cofactor protein (MCP; CD46), complement receptor 1 (CR1; CD35), factor H (FH) and C4b-binding protein (C4BP). Structurally, these proteins are composed of repeating complement control protein (CCP) domains where 2-4 successive domains contribute to the regulatory functions termed as decay-accelerating activity (DAA) and cofactor activity (CFA). However, no four-domain chimeric protein currently exists having both strong DAA (CP-DAA and AP-DAA) and strong CFA (C3b-CFA and C4b-CFA). Therefore, chimeric protein DCP (i.e.