Bone marrow is affected as a somatic dose indicator. Which cell type will be depressed most severely?

• A. Hematological
• B. Red blood cells
• C. Lymphocytes
• D. Platelets

Answer: (C)

Radiosensitivity in blood-forming tissue is driven by how rapidly cells divide. Lymphocytes are among the most radiosensitive cells because they divide frequently and have relatively limited capacity to repair radiation-induced DNA damage. After somatic irradiation, lymphocyte counts drop quickly, producing a pronounced depression in this cell population. In contrast, mature red blood cells are not dividing, so their immediate decline is slower, and while platelet production from megakaryocytes is affected by marrow suppression, the acute, severe decline is seen most with lymphocytes. The broad term hematological isn’t a specific cell type, so it doesn’t pinpoint the affected population. Thus, lymphocytes are the most severely depressed.