Complement Factor D （Adipsin）， which belongs to the trypsin family of peptidases， is involved in the alternative complement pathway of the complement system where it cleaves factor B. In the alternative complement pathway， Adipsin is best known for its role in humoral suppression of infectious agents. In addition， Adipsin is a serine protease which is secreted by adipocytes into the bloodstream. Ultimately， Adipsin has a high level of expression in fat， proposing a role for adipose tissue in immune system biology.
