ECP was first discovered in 1977 and since then, evidence has been gathered to understand its roles in physiology and pathophysiology. ECP is a peptide of 133 a. a., with the first 40 a.a. necessary for membrane interfering, heparin binding and cytotoxic activity. The heparin binding ability of ECP might enable the protein to bind proteoglycans on other human cells for possible uptake [34] or heparan sulfate in extracellular matrix for later use such as is the case for CXCL10 [149] . In a similar manner ECP might bind microorganisms peptidoglycans for uptake and cytotoxicity [32] . The non-synonymous polymorphism rs2073342 reduces cytotoxicity suggesting an alteration of the three-dimensional structure influencing catalytic site elsewhere in the protein. ECP is glycosylated, and as recently discovered can be nitrated. The development of increasingly sophisticated assays will determine whether other modifications, perhaps function associated, are also important in ECP activity.