Which substance is contained in the primary granules of neutrophils?

Neutrophils, a type of white blood cell essential for the innate immune response, contain various granules that store substances important for their function. The primary granules of neutrophils are particularly known for their role in host defense, and myeloperoxidase is a significant enzyme found within these granules.

Myeloperoxidase is involved in the oxidative burst, a critical mechanism through which neutrophils destroy pathogens. This enzyme catalyzes the conversion of hydrogen peroxide into hypochlorous acid, a potent antimicrobial agent that helps neutralize bacteria and fungi. The presence of myeloperoxidase in primary granules underscores its importance in the neutrophil's ability to combat infections effectively.

While lactoferrin, histamine, and alkaline phosphatase are also important substances related to immune function and inflammation — each associated with different types of cells or granules — they do not specifically reside in the primary granules of neutrophils. Lactoferrin is typically found in secondary granules and plays a role in iron sequestration and antimicrobial activity, histamine is mainly found in mast cells and basophils, and alkaline phosphatase is associated with various cell types and functions. Thus, myeloperoxid