Respiratory burst in neutrophils occurs due to
**Core Concept**
Respiratory burst in neutrophils is a process where these cells generate reactive oxygen species (ROS) in response to inflammatory stimuli, leading to the production of superoxides and other reactive intermediates. This process is crucial for the killing of ingested microorganisms within phagosomes. The enzyme responsible for this process is NADPH oxidase, which catalyzes the transfer of electrons from NADPH to oxygen, resulting in the formation of superoxide anion.
**Why the Correct Answer is Right**
The respiratory burst in neutrophils is initiated by the activation of NADPH oxidase, a multi-subunit enzyme complex containing the cytosolic components p47phox and p67phox, and the transmembrane component gp91phox. Upon activation, this enzyme complex translocates to the phagosomal membrane, where it catalyzes the reduction of oxygen to form superoxide anion (O2-). Superoxide anion then dismutates to form hydrogen peroxide (H2O2), which is further converted to hydroxyl radicals (-OH) in the presence of ferrous ions. These reactive oxygen species are toxic to ingested microorganisms and play a crucial role in the defense against infections.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the enzyme responsible for the respiratory burst in neutrophils.
**Option B:** This option is incorrect because it does not specify the involvement of NADPH oxidase in the respiratory burst process.
**Option C:** This option is incorrect because it does not accurately describe the enzyme responsible for the respiratory burst in neutrophils.
**Clinical Pearl / High-Yield Fact**
A key clinical correlation is that the respiratory burst in neutrophils is impaired in patients with chronic granulomatous disease (CGD), a rare genetic disorder characterized by recurrent life-threatening infections with catalase-positive bacteria and fungi.
**Correct Answer: A. NADPH oxidase**