Which cells are phagocytic and derived from monocytes in the blood?

• A. Plasma cells
• B. Lymphocytes
• C. Mast cells
• D. Macrophages

Answer: (D)

Monocytes circulating in the blood differentiate into macrophages once they migrate into tissues. Macrophages are the professional phagocytes of the immune system, engulfing bacteria, dead cells, and debris, and they also play a key role in antigen presentation to T cells. The other options don’t fit because plasma cells arise from B lymphocytes and specialize in antibody production, lymphocytes (T and B cells) are not primarily phagocytic, and mast cells are tissue-resident cells involved in allergic responses and defense but are not derived from monocytes nor primarily phagocytic.