What is a leukocyte?

A leukocyte is defined as a white blood cell, which plays a crucial role in the immune system by fighting infections and other diseases. These cells are essential for the body's defense mechanisms and are involved in identifying and destroying pathogens such as bacteria and viruses. They also help in the response to foreign substances and assist in immune regulation and inflammation.

Understanding leukocytes as white blood cells provides insight into their key functions, including their ability to circulate throughout the bloodstream and migrate to tissues where they are needed to respond to threats. This differentiation is vital in medical contexts, as various types of leukocytes, such as lymphocytes, neutrophils, and monocytes, each perform specific roles within the overall immune response.

The other terms in the question refer to different components of blood. Red blood cells are primarily responsible for transporting oxygen, platelets are crucial for blood clotting, and clotting factors are proteins that help control bleeding. Therefore, recognizing leukocytes as white blood cells highlights their specific function in the immune response, making the correct answer clear.