Also known as complement factor D. It is a protein that is a member of the trypsin family of peptidases. It is a component of the alternative complement pathway best known for its role in the humoral suppression of inflammation by infectious agents. The protein is also a serine protease that is secreted by adipocytes into the bloodstream. It has a high level of expression in the fat pads and may play a role in the association of the inflammatory response associated with obesity.