Subcellular fractionation of human neutrophils and analysis of subcellular markers.

The neutrophil has long been recognized for its impressive number of cytoplasmic granules that harbor proteins indispensable for innate immunity. Analysis of isolated granules has provided important information on how the neutrophil grades its response to match the challenges it meets on its passage from blood to tissues. Nitrogen cavitation was developed as a method for disruption of cells on the assumption that sudden reduction of the partial pressure of nitrogen would lead to aeration of nitrogen dissolved in the lipid bilayer of plasma membranes. We find that cells are broken by the shear stress that is associated with passage through the outlet valve under high pressure and that this results in disruption of the neutrophil cell membrane while granules remain intact. The unique properties of Percoll as a sedimentable density medium with no inherent tonicity or viscosity are used for creation of continuous density gradients with shoulders in the density profile created to optimize the physical separation of granule subsets and light membranes. Immunological methods (sandwich enzyme-linked immunosorbent assays) are used for quantitation of proteins that are characteristic constituents of the granule subsets of neutrophils.