The most common white blood cell and your immune system’s first responder—it arrives fast, kills pathogens, and dies quickly.Neutrophils are the most abundant circulating leukocytes and primary effectors of acute innate immunity. They kill pathogens through phagocytosis, degranulation (releasing antimicrobial peptides including alpha-defensins HNP-1–4), reactive oxygen species production, and neutrophil extracellular trap (NET) formation. Neutrophil alpha-defensins constitute 5–7% of total neutrophil protein. Excessive neutrophil activation contributes to inflammatory tissue damage; insufficient neutrophil function increases infection susceptibility.