Which white blood cell is the largest circulating leukocyte with a kidney-shaped nucleus and differentiates into macrophages?

Which white blood cell is the largest circulating leukocyte with a kidney-shaped nucleus and differentiates into macrophages?

• A. Lymphocytes
• B. Megakaryocyte
• C. Monocytes
• D. Platelets

Answer: (C)

Monocytes are the largest circulating white blood cells. They have a kidney-shaped (reniform) nucleus, which helps distinguish them from other leukocytes. When they leave the bloodstream and enter tissues, they differentiate into macrophages, becoming powerful phagocytes that ingest pathogens and debris and also present antigens to T cells to help drive the adaptive immune response. Lymphocytes are generally smaller with a round nucleus; megakaryocytes stay in the bone marrow and produce platelets, which are tiny cell fragments, not circulating leukocytes. So the combination of large size, kidney-shaped nucleus, and the ability to differentiate into macrophages points to monocytes.

Monocytes are the largest circulating white blood cells. They have a kidney-shaped (reniform) nucleus, which helps distinguish them from other leukocytes. When they leave the bloodstream and enter tissues, they differentiate into macrophages, becoming powerful phagocytes that ingest pathogens and debris and also present antigens to T cells to help drive the adaptive immune response. Lymphocytes are generally smaller with a round nucleus; megakaryocytes stay in the bone marrow and produce platelets, which are tiny cell fragments, not circulating leukocytes. So the combination of large size, kidney-shaped nucleus, and the ability to differentiate into macrophages points to monocytes.