Subcellular fractionation of neutrophils. Isolated neutrophils, either unstimulated (black lines) or stimulated by 1.0 μmol/L Ionomycin (gray lines) were cavitated and fractionated on a 3-layer Percoll density gradient. Fractions were collected from the bottom of the centrifuge tube and assayed for the following proteins: Myeloperoxidase (azurophil granules. Peak indicated by open arrow marked A). Lactoferrin (specific granules, □). Gelatinase (gelatinase granules, X). Latent alkaline phosphatase (secretory vesicles. Peak indicated by open arrow marked S). HLA (plasma membranes. Peak indicated by open arrow marked P) and hCAP-18 (o). Values are given as μg/mL. Insert: Immunoblot of control cells with anti-hCAP-18 antibody. MW marker indicated by solid arrows.