Eosinophils have occasionally been found to infiltrate developing tumours and have been suggested to have a role in fighting these malignancies [122] . The involvement of the eosinophils have been suggested by the finding of elevated sECP levels in patients with renal tumours (table 1) [123] . ECP assayed in urine from patients with urinary bladder tumours showed a twofold increase compared to normal's [124] . The elevated levels suggest presence of activated eosinophils in some patients with these malignancies. In the analysis of the possible involvement of ECP in tumour defence, ECP has been evaluated in respect of altering proliferation of various cell lines. The cell lines K562 and HL-60 were incubated with 1.1 uM (21 ug/mL) ECP and the cell line A431 with 4 μM (76 ug/mL) and this resulted in 50 percent inhibition of proliferation after four days. To analyse whether growth inhibition was related to positive charge or RNase activity, poly-lysine or RNase A was used with no effect [34] . ECP exists in two forms dependent on a polymorphism, R97 and T97. It was found that the T97 form had reduced capability to kill K562 and NCI-H69 cells [36] . These recombinant (r) ECPs were produced in a baculovirus system and deglycosylation restored the cytotoxic activity.