Which of the following describes a neutrophil?
a. ?abundant, agranular, especially effective against cancer cells
b. ?abundant, granular, especially effective against bacteria
c. ?rare, agranular, releases antimicrobial defensins
d. ?rare, granular, contains multiple granules packed with histamine
.
The Correct Answer and Explanation is:
Correct Answer:
b. abundant, granular, especially effective against bacteria
Explanation (Approx. 300 words):
Neutrophils are the most abundant type of white blood cells (WBCs) in the human body, making up approximately 50–70% of all circulating leukocytes. As granulocytes, they contain numerous cytoplasmic granules filled with enzymes and antimicrobial substances, which are critical to their role in the innate immune response.
Neutrophils are especially effective against bacteria, which makes them a first line of defense during bacterial infections. They are typically the first immune cells to arrive at the site of infection or injury. Neutrophils identify and engulf pathogens via phagocytosis, then destroy them using reactive oxygen species and enzymes like lysozyme, myeloperoxidase, and defensins released from their granules.
In addition to phagocytosis, neutrophils can release neutrophil extracellular traps (NETs)—web-like structures composed of DNA and proteins—that trap and kill microbes extracellularly.
Neutrophils are short-lived (about 6–8 hours in the bloodstream) but produced in vast numbers daily in the bone marrow. Their elevated count in blood, known as neutrophilia, typically indicates a bacterial infection or inflammation.
Let’s briefly evaluate the other choices:
- a. abundant, agranular, especially effective against cancer cells: Incorrect. While abundant might apply, neutrophils are granular, not agranular, and their primary role is fighting bacteria, not specifically cancer cells.
- c. rare, agranular, releases antimicrobial defensins: Incorrect. Neutrophils are not rare and do release defensins, but they are granular.
- d. rare, granular, contains multiple granules packed with histamine: Incorrect. This describes basophils, which are involved in allergic reactions and inflammation, not neutrophils.
In conclusion, option b correctly identifies neutrophils as abundant, granular, and especially effective against bacteria, reflecting their essential function in immune defense.
