Dying and Necrotic Neutrophils Are Anti-Inflammatory Secondary to the Release of α-Defensins

Neutrophils are recruited to sites of injury but their timely removal is thought to be vital to prevent exacerbating inflammation. In addition, the recognition of apoptotic cells by cells of the innate immune system provides potent anti-inflammatory and anti-immunogenic signals. In this article, we describe how human neutrophils dying by apoptosis or necrosis release anti-inflammatory peptides, the alpha-defensins. This family of small cationic peptides effectively inhibits the secretion of multiple proinflammatory cytokines and NO from macrophages, the main innate immune cell found at sites of chronic inflammation. In addition, the systemic administration of necrotic neutrophil supernatants and a-defensins protects mice from a murine model of peritonitis. Hence. their effects may be far-reaching and serve to kill microbes while regulating a potentially tissue-destructive inflammatory response. The Journal of Immunology, 2009, 183: 2122-2132.