Neutrophil-Derived Granule Products
Neutrophils are also a source of specialized products that can amplify immune responses. Many antimicrobial polypeptides are present in neutrophilic granules. The principal ones are bactericidal/permeability-increasing protein, defensins, lysozyme, lactoferrin, and the serine proteases.
In addition to antimicrobial polypeptides, neutrophils contain numerous other molecules that may contribute to inflammation. These compounds include hydrolytic enzymes, elastase, metalloproteinases, gelatinase, myeloperoxidase, vitamin B12–binding protein, cytochrome b558, and others. Granule contents remain inert and membrane-bound when the granules are intact and become active and soluble when granules fuse to the phagocytic vesicles or plasma membrane.
An example of a neutrophil-derived granule product is collagenase. Various forms of collagenase contribute to corneal injury and liquefaction during bacterial keratitis and scleritis, especially in infections with Pseudomonas species. Collagenases also contribute to peripheral corneal melting syndromes secondary to rheumatoid arthritis–associated peripheral keratitis.
Excerpted from BCSC 2020-2021 series: Section 9 - Uveitis and Ocular Inflammation. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.