Which of the following is true about white blood cells?

White blood cells, or leukocytes, play a crucial role in the immune system by helping to protect the body against pathogens such as bacteria, viruses, and other foreign invaders. They are essential components of the body's defense mechanism and are involved in identifying, attacking, and neutralizing these harmful organisms. There are various types of white blood cells, each with specific functions in the immune response, including lymphocytes, monocytes, neutrophils, and eosinophils. Their ability to recognize and respond to pathogens is vital for maintaining health and preventing infections.

Transporting oxygen is a function associated with red blood cells, while blood clotting is primarily the role of platelets, a different component of the blood. Although white blood cells can be found in lymph nodes, they are not primarily localized there, as they circulate throughout the bloodstream and can be distributed in various tissues in the body to ensure a rapid immune response where needed.