C3 and leishmaniasis: The GP63 expressed by Leishmania, an intracellular protozoa that causes leishmaniasis, is the most abundant surface glycoprotein on Leishmania promastigotes (Yao et al., 2003) that binds to C3 with high affinity, leading to proteolysis of the active component C3b to form the inactive iC3b, thus preventing the formation of C3-convertase (Yao, 2010).