Role of granule proteins in microbial killing

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. 

The secretory vesicles have recently been discovered by Borregaard and co-workers (Sengelpv, Nielson Borregaard, 1992). These are very difficult to separate from the plasma membrane on density gradients. They possess latent alkaline phosphatase activity (i.e. subcellular fractions must be incubated with detergents such as Triton to release activity) and albumin, whilst the membranes contain CR1, CR3 and the fMet-Leu-Phe receptor. They are endocytic vesicles but can be rapidly translocated to the plasma membrane. 

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