A left shift on the WBC differential indicates an increase in which cells?

A left shift on the WBC differential indicates an increase in which cells?

• A. Eosinophils
• B. Lymphocytes
• C. Monocytes
• D. Neutrophils

Answer: (D)

A left shift on the WBC differential signals the bone marrow is rapidly releasing neutrophils in response to acute stress, infection, or inflammation, so you see more neutrophils in the blood, often with immature forms called bands. Neutrophils are the first responders to bacterial invasion, so an increase reflects an active neutrophil-driven response. Eosinophils, lymphocytes, and monocytes each rise or fall in different contexts (such as allergies or parasitic infections, viral infections, or chronic inflammation), but they don’t produce the characteristic left shift. Therefore, the increase is in neutrophils.

A left shift on the WBC differential signals the bone marrow is rapidly releasing neutrophils in response to acute stress, infection, or inflammation, so you see more neutrophils in the blood, often with immature forms called bands. Neutrophils are the first responders to bacterial invasion, so an increase reflects an active neutrophil-driven response. Eosinophils, lymphocytes, and monocytes each rise or fall in different contexts (such as allergies or parasitic infections, viral infections, or chronic inflammation), but they don’t produce the characteristic left shift. Therefore, the increase is in neutrophils.