What is the main function of leukocytes?

Leukocytes, also known as white blood cells, play a crucial role in the immune system by protecting the body against invading microorganisms, such as bacteria, viruses, and parasites. They are essential for identifying and responding to foreign pathogens, thus fostering the body’s defense mechanisms. There are several types of leukocytes, each with specific functions, including the ability to engulf and destroy pathogens, produce antibodies, and coordinate immune responses.

The other options address different physiological functions: initiating blood clotting involves platelets and clotting factors; transporting carbon dioxide is primarily the role of red blood cells, which carry oxygen and return carbon dioxide to the lungs; and regulating blood pressure involves various mechanisms including the action of hormones and the diameter of blood vessels. Therefore, the primary purpose of leukocytes is indeed to protect the body, highlighting their integral role in maintaining health and fighting infections.