Which of the following are referred to as mononuclear phagocytes?

• A. Lymphocytes and basophils.
• B. Mast cells and eosinophils.
• C. Basophils and eosinophils.
• D. Monocytes and macrophages.

Answer: (D)

Verified step by step guidance

1. Understand the term 'mononuclear phagocytes': these are immune cells characterized by having a single, non-lobed nucleus and the ability to engulf and digest pathogens or debris (phagocytosis).
2. Identify the cell types listed in the options and classify them based on their nucleus type and function: lymphocytes (mononuclear, but not primarily phagocytic), basophils (multilobed nucleus, involved in allergic responses), mast cells (similar to basophils, involved in allergy and inflammation), eosinophils (bilobed nucleus, involved in parasitic infections and allergy), monocytes (mononuclear and phagocytic), macrophages (derived from monocytes, mononuclear and highly phagocytic).
3. Recognize that monocytes and macrophages fit the definition of mononuclear phagocytes because they have a single nucleus and perform phagocytosis effectively.
4. Exclude other cell types like lymphocytes, basophils, mast cells, and eosinophils because they either do not perform phagocytosis as their primary function or have multilobed nuclei.
5. Conclude that the correct answer is 'Monocytes and macrophages' as they are the classic examples of mononuclear phagocytes.