What is the function of leukocytes?

Leukocytes, commonly known as white blood cells, play a crucial role in the immune system. Their primary function is to defend the body against diseases and infections caused by pathogens such as bacteria, viruses, fungi, and parasites. Leukocytes identify and neutralize foreign invaders through various mechanisms including phagocytosis, where they engulf and digest harmful organisms, and the production of antibodies, which specifically target pathogens.

Each type of leukocyte, such as neutrophils, lymphocytes, and monocytes, has specialized functions that contribute to the overall immune response. For instance, lymphocytes are key in recognizing specific antigens, while neutrophils respond rapidly to infections and act as the first line of defense.

The other options describe functions that are carried out by different cells or systems in the body. For example, the transportation of nutrients is primarily the job of red blood cells and the circulatory system; regulating blood pressure involves the work of the cardiovascular system, specifically the heart and blood vessels; and the process of digestion is predominantly managed by the gastrointestinal system with the help of digestive enzymes and other specialized cells.