**Core Concept**
Myeloperoxidase (MPO) is an enzyme found in neutrophil granules that plays a crucial role in the antimicrobial activity of neutrophils. It catalyzes the production of hypochlorous acid from hydrogen peroxide and chloride ions, which is essential for killing bacteria and other pathogens.

**Why the Correct Answer is Right**
In genetic deficiency of MPO, the neutrophils are unable to produce hypochlorous acid, leading to impaired antimicrobial activity. This results in increased susceptibility to infections, particularly those caused by bacteria and fungi. The deficiency affects the ability of neutrophils to kill pathogens, making it difficult for the host to defend against infections.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not directly relate to the function of MPO in antimicrobial activity.
**Option B:** This option is incorrect because it refers to a different enzyme involved in a different pathway. While it may have some indirect effects on the immune system, it is not directly related to the increased susceptibility to infections in MPO deficiency.
**Option C:** This option is incorrect because it refers to a different type of immune cell that is not directly affected by MPO deficiency.

**Clinical Pearl / High-Yield Fact**
MPO deficiency is a rare genetic disorder that increases the risk of recurrent infections, particularly those caused by Staphylococcus aureus and other gram-positive bacteria.

**Correct Answer: C. Impaired neutrophil function**