Which component of blood helps to fight infections?

White blood cells are a key component of the immune system, and their primary function is to help the body fight infections. These cells are integral in recognizing and responding to pathogens, such as bacteria, viruses, and other foreign substances that can cause illness. When an infection occurs, white blood cells are activated and mobilized to the site of infection to eliminate harmful invaders through various mechanisms, including phagocytosis and the production of antibodies.

In contrast, platelets play a vital role in blood clotting, helping to prevent excessive bleeding when injuries occur. Red blood cells are primarily responsible for transporting oxygen from the lungs to the body's tissues and returning carbon dioxide to the lungs for exhalation. Plasma, the liquid component of blood, serves as a medium for transporting nutrients, hormones, and waste products but does not directly combat infections. Hence, white blood cells are essential for immune defense, making them the correct choice when identifying the component of blood that fights infections.