Eosinophils are found lining and degranulating in both the respiratory and gastrointestinal mucosa [50] . Eosinophils are generally not thought of as defendants during bacterial inflammation. However sECP has been found elevated in septic patients [76] and very high levels of ECP in nasal secretions from patients with normal cold (13 μg/mL) or severe community acquired rhinosinusitis has been described in one case (11.7 μg/mL, table 1) [77] . Moreover, a recent study has shown that eosinophils expel mitochondrial DNA coated with ECP and other granule proteins which are bactericidal in mice in vivo [134] . Additionally, a few studies have described neutrophils producing ECP [15] . In view of these findings the anti -bacterial properties of ECP has been evaluated. Bacterial strains chosen for analysis were Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). High levels of ECP (50 μg/ mL) decreased the number of colony-forming units (cfu) by 72 percent and close to 100 percent, respectively, for the two strains after a very short 2 hr of incubation. ECP only killed E. coli growing in logarithmic phase and acted on both the inner and outer membranes of E. coli [135] . Recombinant ECP was also cytotoxicity to S. aureus. Overnight incubation of rECP with the bacteria (16 kDa, 16 ug/ mL/1 uM) left 35 percent of the cfu. rECP in which a.a.'s involved in RNase activity had been substituted (K38R and H128D), terminating the RNase activity, had no effect on the bacterial killing activity [21] . In conclusion therefore, eosinophils and ECP might have a role in bacterial defence. Due to its stability, it might be feasible to speculate that ECP over time accumulate in mucus fluids such as nasal secretions and act as a first line of defence against bacterial intrusion.