What is the main function of leukocytes in the body?

The main function of leukocytes, also known as white blood cells, is to fight infection. These cells are a crucial component of the immune system and play a vital role in the body's defense against pathogens such as bacteria, viruses, and other foreign invaders. When an infection occurs, leukocytes can quickly identify and target the harmful microorganisms, helping to eliminate them and protect the body from disease. They do this through various mechanisms, including producing antibodies, directly attacking infected cells, and orchestrating the overall immune response.

In contrast, the other options focus on different functions in the body. For example, the transport of oxygen is primarily carried out by red blood cells, which contain hemoglobin. Hormonal regulation is mainly the responsibility of the endocrine system, which uses various glands to secrete hormones into the bloodstream. Digesting food is the function of the digestive system, involving organs such as the stomach and intestines breaking down food into nutrients. Therefore, the role of leukocytes is uniquely positioned as key players in immunity and infection control within the body.