Question

How much percentage of white blood cells do monocytes make up of ?

• A. 0% \(-\) 3%
• B. 100%
• C. 50% \(-\) 70%
• D. 5% to 10%

Hint:

Use the popular mnemonic "Never Let Monkeys Eat Bananas" to remember the order of abundance of white blood cells:
Neutrophils (highest), Lymphocytes, Monocytes, Eosinophils, Basophils (lowest).

Answer 1

The Correct Option is D

Step 1: Concept:
The question asks for the normal relative percentage of a specific leukocyte subtype (monocytes) within the total white blood cell (WBC) population in a healthy human differential blood count.

Step 2: Step-by-step Explanation:

• White blood cells (leukocytes) are categorized broadly into granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes).

• In a standard complete blood count (CBC) with differential, the relative proportions of these cells are rigorously analyzed.

• Neutrophils: These are the most abundant WBCs, rapidly responding to acute bacterial infections, and normally constitute 50% - 70% of the total WBC count. (Option C represents neutrophils).

• Lymphocytes: These mediate the adaptive immune response (T-cells, B-cells) and typically make up 20% - 40% of the count.

• Monocytes: Monocytes are the largest circulating white blood cells. They circulate in the bloodstream for several days before migrating into tissues, where they differentiate into highly phagocytic tissue-resident macrophages or dendritic cells.

• In a healthy individual, monocytes typically comprise 2% to 8% (or frequently cited up to 10%) of the total leukocyte population.

• Eosinophils and Basophils: Eosinophils generally make up 1% - 4% (Option A is close to this), and basophils are the rarest at \(<\)1%.

• Matching these physiological facts with the options, Option (D) "5% to 10%" is the accepted standard reference range for circulating monocytes.

Step 3: Final Answer:
Monocytes normally account for 5% to 10% of total white blood cells.