Neutrophil granules in health and disease

The granules of the neutrophil, in addition to contributing to its distinctive morphologic appearance, are critical to its unique functions. Specific granules appear necessary for neutrophil recruitment to sites of inflammation, for upregulation of receptors important in the control of chemotaxis and the respiratory burst, for disaggregation, for bactericidal activity, and for chemoattractant generation. The azurophilic granules supply enzymes for digestive and bactericidal functions and supply MPO to the MPO-halide-hydrogen peroxide bactericidal system. Azurophilic granule contents also regulate inflammation by degrading inflammatory products. Both granules may play a role in intracellular calcium regulation. In addition to these activities that protect the host from infection, granules also, under certain circumstances, contribute to disease processes. For these reasons, greater knowledge about granule contents, control of degranulation, inactivation of toxic granule contents and products, and the role of granules in neutrophil membrane events and function has widespread implications for treatment of patients with neutrophil dysfunction syndromes and patients with multiple other systemic diseases.