Properdin is also known as Complement factor P, CFP, PFC, a positive regulator of the alternate pathway of complement. It binds to and stabilizes the C3- and C5-convertase enzyme complexes. Properdin is produced by many different leukocyte subsets and circulates as cyclic oligomers of monomeric subunits. Properdin on platelet/granulocyte aggregates(PGA) formation are tightly regulated by Factor H, properdin enhances PGA formation via increased production of C5a, and that inhibition of properdin function has therapeutic potential to limit thromboinflammation in diseases characterized by increased PGA formation.