Neutrophil cytosol factor 1( NCF1) is a 47 kDa cytosolic subunit of neutrophil NADPH oxidase. This oxidase is characterized as a multicomponent enzyme which is activated to produce superoxide anion. NCF2, NCF1, and a membrane bound cytochrome b558 are required for the activation of the latent NADPH oxidase. The human NCF1 gene encodes a 390 amino acids protein without a signal peptide. The NCF1 gene interacts with other subunits of nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) and plays an important role in innate immunity, producing reactive oxygen species and reducing the severity and duration of parasitic infection and autoimmune disease. NCF1 also has a role in T cell activation.