Subcellular fractionation of resting, FMLP-activated, and phagocytosing human PMNs. Distribution profiles of neutral sphingomyelinase, HLA, and latent alkaline phosphatase. Cells were processed for fractionation as described in Experimental Procedures and in the legend to Fig 3. Fractions were assayed for neutral sphingomyelinase activity, myeloperoxidase, lactoferrin, gelatinase, HLA class I, and latent alkaline phosphatase. Numbers are the average of three experiments (same data as shown in Fig 3), normalized to a cell number of 3 × 108 cells, and expressed in percent of the total amount measured in fractions 1 through 25. Latent alkaline phosphatase is only shown in control cells, because secretory vesicles are almost completely mobilized (and latent AP thus disappearing) after FMLP stimulation. The localization of the majority of azurophil granules (AG) and specific/gelatinase granules (SG+GG) is marked.
