How many types of white blood cells are described, and what are their names?

• A. Four: Neutrophils, Eosinophils, Basophils, Lymphocytes.
• B. Five: Basophils, Eosinophils, Neutrophils, Monocytes, and Lymphocytes.
• C. Six: Add Macrophages to the list.
• D. Three: Neutrophils, Lymphocytes, Monocytes.

Answer: (B)

Five major types of white blood cells are typically described in peripheral blood: neutrophils, eosinophils, basophils, monocytes, and lymphocytes. Macrophages come from monocytes and reside in tissues, so they aren’t counted as a separate circulating white blood cell type in standard classifications. Each type has a distinct role: neutrophils are quick responders to bacterial infection; eosinophils defend against parasites and participate in allergic responses; basophils release histamine during inflammation; monocytes travel in the blood and differentiate into macrophages or dendritic cells in tissues, performing phagocytosis and antigen presentation; lymphocytes—including T cells, B cells, and natural killer cells—coordinate immune responses and antibody production. This five-type grouping is the most accurate description for circulating white blood cells; including macrophages as a separate type or omitting monocytes would miss key parts of the immune response.