What role do white blood cells play in the immune system?

White blood cells, also known as leukocytes, are a crucial component of the immune system, playing a primary role in defending the body against pathogens such as bacteria, viruses, and other foreign invaders. They identify, target, and eliminate harmful organisms, thus helping to maintain the body's health and prevent infections.

There are several types of white blood cells, each with specific functions in the immune response. For example, some white blood cells, like lymphocytes, are responsible for producing antibodies that neutralize pathogens, while others, like phagocytes, can ingest and destroy these invaders directly. This defensive capability is vital for protecting the body from diseases and facilitating the healing process after infections or injuries.

In contrast, other options refer to functions not associated with white blood cells. For example, the transport of oxygen in the blood is the function of red blood cells, while hormone production is typically the role of glands and specialized cells in the endocrine system. Digestion is primarily managed by the digestive system, involving organs like the stomach and intestines, rather than the immune function of white blood cells.