Which type of blood cells is essential for a properly-functioning immune system?

White blood cells, also known as leukocytes, play a critical role in the immune system by defending the body against infectious diseases and foreign invaders. They are involved in various immune responses, including recognizing pathogens, producing antibodies, and coordinating the activities of other immune cells.

Different types of white blood cells serve specific functions. For example, lymphocytes (which include B cells and T cells) are crucial for adaptive immunity, while phagocytes like neutrophils and macrophages are key players in the innate immune system, actively engulfing and destroying pathogens.

In contrast, red blood cells are primarily responsible for transporting oxygen from the lungs to the body's tissues and returning carbon dioxide from the tissues to the lungs. Plasma is the liquid component of blood that carries cells and helps with nutrient transport, while platelets are essential for blood clotting and wound healing. None of these components play a direct role in the immune response like white blood cells do. Hence, white blood cells are indispensable for a properly functioning immune system.