Band form of neutrophilic granulocyte

Scheme electron microscopy. From CFU-S (colony forming units-spleen) stem cells arise CFU-GM (colony forming unit-granulocyte/monocyte) stem cells. The latter divide by mitoses and differentiate via promyeloblasts and myeloblasts into neutrophilic myelocytes (the last proliferative stage). The next stages are postmitotic cells, called neutrophilic metamyelocytes that differentiate into band forms and mature segmented forms of neutrophilic granulocytes. These cells are also called polymorphonuclear neutrophils (PMN), polymorphonuclear leukocytes or polymorphs, neutrophils. During that differentiation process nuclear indentations in neutrophilic myelocytes appear and they become more distinct in later stages (metamyelocytes) resulting in horseshoe shaped nuclei (band forms) and eventually into nuclear lobes (mature forms). Band forms (9-12 μm) are the earliest stages of the two-lobed granulocytes. The horseshoe shaped nucleus is irregularly indicating future lobulation. There are few organelles as well as granules of varying sizes and densities. The primary ('non-specific' or azurophilic) granules are electron-grey (2) and contain peroxidase, lysozyme, various hydrolytic enzymes among others acid phosphatase and arylsulfatase. The secondary (specific) electron-dense granules (1) contain lysozyme and phagocytin, collagenase, lactoferrin. Both primary and secondary granules fuse with phagosomes, whose content are then digested and eliminated much similar as in macrophages.