NCF4 (Neutrophil Cytosolic Factor 4): NCF4 is a part of the NADPH oxidase complex that plays a crucial role in the immune defence system. It helps regulate the formation and activation of this complex, allowing the production of reactive oxygen species (ROS) during the oxidative burst in phagocytes. This process is vital for destroying engulfed pathogens, and mutations in NCF4 can weaken immunity, leading to increased vulnerability to infections.