Neutrophil migration generates CEP formation. (A) Neutrophils were isolated from human blood and labeled with green fluorescent dye PKH67. Fibrin gel supplemented with 1% fetal bovine serum and 100 ng/mL LPS was polymerized in a Boyden chamber. Labeled neutrophils were plated on top of the fibrin gel in the lower chamber. Migration was initiated by adding 100 nM FMLP to the upper chamber. After 18 hours, the gel was fixed and stained with anti-CEP antibody (red). Control fibrin gel was incubated without neutrophils. (B) Quantification of intensity of CEP staining of 15 fields in 3 samples was detected by confocal microscopy. (C) Separated samples after migration were digested using plasmin and analyzed by SDS-electrophoresis and western blot using anti-CEP antibody. DD- fragment of fibrin (180 kDa). E-fragment of fibrin (55 kDa). (D) CEP formation was inhibited in the presence of MPO inhibitor, 4-ABH, but was not affected by eosinophil peroxidase inhibitor, resorcinol. (E) Accumulation of CEP but not EP is aided by MPO. Wounded tissues were collected from WT and MPO-deficient mice and stained for EP and CEP. *P < .05; **P < .01. LPS, lipopolysaccharide.