Which type of blood cell primarily defends the body against infection?

White blood cells, also known as leukocytes, play a crucial role in the immune system. They are specifically designed to identify and combat pathogens such as bacteria, viruses, and other foreign invaders in the body. There are different types of white blood cells, including lymphocytes (T cells and B cells), neutrophils, basophils, eosinophils, and monocytes, each with distinct functions in immune defense.

Unlike red blood cells, which are primarily responsible for transporting oxygen from the lungs to tissues and carbon dioxide from the tissues back to the lungs, or platelets, which play a key role in blood clotting, white blood cells are specialized for immune response. Plasma cells, derived from B lymphocytes, produce antibodies that target specific antigens, contributing to the immune response, but they are a subset of the broader category of white blood cells.

Thus, the correct answer emphasizes the central role of white blood cells in defending the body against infection, showcasing their importance in maintaining health and fighting disease.