What is the main function of white blood cells in the body?

White blood cells, also known as leukocytes, play a crucial role in the body’s immune system. Their primary function is to defend the body against infections and foreign invaders such as bacteria, viruses, and parasites. When pathogens enter the body, white blood cells are activated and mobilize to the site of infection, where they work to neutralize and eliminate the threat. This process involves various types of white blood cells, each with specific functions, such as phagocytosis (the engulfing of pathogens) and the production of antibodies.

The other options listed refer to different physiological functions in the body. Carrying oxygen is the primary responsibility of red blood cells. The regulation of blood sugar levels involves hormones produced by the pancreas, like insulin. Transporting nutrients to cells is a function primarily associated with the circulatory system, particularly through plasma and other components. Each of these processes is vital for maintaining overall health, but they do not relate to the immune functions provided by white blood cells. This clear differentiation underscores the essential role white blood cells play in protecting the body from various diseases.