Late band-form of neutrophilic granulocyte (peripheral blood, human)

Electron microscopy. Band forms (9-12 μm) are the earliest stages of the motile two-lobed granulocytes. The horseshoe shaped nucleus (3) is irregularly and indicates progressing lobulation. The neutrophil contains many granules of varying sizes and densities. On base of routine electron microscopy primary and secondary granules can be discerned. The primary, spherical to ellipsoid granules (1) are (lightmicroscopic) azurophilic granules, (diameter 0.4 μm) (arrows). They contain e.g. acid hydrolases as acid phosphatase, arylsulfatase, glucuronidase, but also myeloperoxidase as an antibacterial substance. The smaller, secondary or specific granules (2) are of varying forms (↓ dumb-bell form) and sizes, (diameter 0.2 μm up to length 0.8 μm). They contain substances like lysozyme, phagocytin to be secreted extracellularly involved in mobilization of inflammatory mediators and complement activation.