Azurophil granules

These more mature cell types are incapable of division and are identified by their nuclear morphology, granule content and accumulation of glycogen particles. In a mature neutrophil there are 200-300 granules, with the specific granules being about twice as abundant as azurophilic granules. 

The antimicrobial neutrophil proteins are located within intracellular granules. Approximately 30% of all neutrophil granules contain myeloperoxidase, and these azurophilic granules are the first granule types to be... 

The peroxidase-negative granules produced later in neutrophil development are termed secondary or specific granules (because they stain only with specific dyes). They are twice as abundant in the cytoplasm of the mature neutrophil as the azurophilic granules. Specific granules contain much of the lysozyme, lactoferrin, vitamin-B 12-binding protein, adhesin receptors, fMet-Leu-Phe receptors, and cytochrome b.245. 

BPI has been purified and characterised from both human and rabbit neutrophils, and the two proteins from these different species are highly homologous the first 17 amino-terminal amino acids are 80% homologous and the two molecules are immunologically cross-reactive. BPI is tightly associated with the azurophilic granule for two reasons ... 

Cathepsin G, a cationic, glycosylated protein of relative molecular mass -27 kDa, exists in four isoforms (25-29 kDa) that are identical in amino acid sequence but differ in levels of glycosylation. It is a component of azurophilic granules and present in human neutrophils at 1.5-3 jug/106 cells, but at lower levels in monocytes. cDNA has been cloned and sequenced (and the amino acid sequence predicted), and the gene has been localised to chromosome 14ql 1.2. The gene comprises five exons and four introns, a structure similar to that of the elastase gene. 

In order to function efficiently, myeloperoxidase must be translocated from its intracellular location, the azurophilic granule, to the site of NADPH oxi-... 

Morphology Lymphocytes possess a large nucleus with little to no basophilic cytoplasm. Differences are seen in the nuclear (N) to cytoplasmic ratio, the degree of cytoplasmic staining with histological dyes and the presence or absence of azurophilic granules. 

MPO is an abundant azurophil granule product and ANCA auto-antigen which is found immunologically (16-29mg/ml synovial fluid) in all rheumatoid fluids [17]. Interestingly, only a minority of the synovial fluid specimens contained any MPO activity [17], Since MPO released from degranulating stimulated PMNs into the extracellular milieu is oxidatively inactivated... 

R4. Ransom, J. T., and Reeves, J. P., Accumulation of amino acids within intracellular lysosomes of rat polymorphonuclear leukocytes incubated with amino acid methyl esters. Evidence for the internal acidification of azurophilic granules. J. Biol. Chem. 258, 9270-9275 (1983). 

Human leukocyte elastase (HLE EC 3.4.21.37 also known as human neutrophil elastase, HNE) [1] is a strongly basic glycoprotein which is produced by polymorphonuclear leukocytes (neutrophils) and is released from their azurophilic granules [2]. HLE exists as at least four distinct isozymes, which range in molecular weight from 24 [3] to 30 kDa [4] and appear to differ only in carbohydrate content [5]. Furthermore, human sputum elastase (HSE), which is isolated from purulent sputum as at least five distinct isozymes [6], is both immunologically and catalytically indistinguishable from HLE [7] and is believed to be identical to it. 

Myeloperoxidase resides in a vesicle in the neutrophil called the azurophilic granule. This vesicle fuses with the phagocytic vesicle, which contains the bacte-rium exposing the bacterium to the enzyme as well as to its toxic product. 

The azurophil granule of the neutrophil is also a rich source of cytocidal proteins, although some of these have received relatively little attention as a mechanism of inflammatory cell-induced lung injury compared with the wealth of literature concerning oxidants and eosinophil-derived proteins. Several difierent cytocidal polypeptides... 

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