ASCP Phlebotomy Technician Certification Practice Exam 2026 – Comprehensive All-in-One Study Guide for Success!

Leukocytes, commonly known as white blood cells, are key components of the immune system. Their primary function is to protect the body from infections and foreign invaders such as bacteria, viruses, and parasites. They play a crucial role in immune response by identifying and destroying pathogens, as well as coordinating the activity of other immune cells.

Leukocytes can be further classified into different types, such as lymphocytes (which include T cells and B cells), neutrophils, monocytes, eosinophils, and basophils, each with specialized functions that contribute to the overall effectiveness of the immune response. For example, lymphocytes are central to the adaptive immune response, while neutrophils are often among the first responders to sites of infection.

In contrast, other body functions listed, like oxygen transport, blood clotting, and nutrient absorption, are primarily managed by other components of the blood or specific systems in the body. Red blood cells are responsible for carrying oxygen; platelets and clotting factors contribute to the blood clotting process; and the digestive system, rather than leukocytes, is responsible for nutrient absorption. Therefore, the involvement of leukocytes in the immune response is the reason why this option is correct.