Which blood component is primarily responsible for immunity?

Leukocytes, also known as white blood cells, are the blood component primarily responsible for immunity. They play a crucial role in the body's defense mechanisms against infections and diseases. There are several types of leukocytes, including lymphocytes, monocytes, and neutrophils, each with specific functions in immune response. For instance, lymphocytes are vital in recognizing and targeting pathogens such as bacteria and viruses, while neutrophils are frontline defenders that quickly respond to infections by engulfing and destroying pathogens.

In contrast, other blood components have different primary functions that do not directly relate to immunity. Platelets are essential for blood clotting, helping to prevent excessive bleeding, while red blood cells are responsible for transporting oxygen from the lungs to the tissues and returning carbon dioxide to the lungs for exhalation. Plasma, the liquid component of blood, serves various purposes, including carrying nutrients, hormones, and waste products, but it is not directly involved in the immune response. Thus, leukocytes are central to the immune system's ability to protect the body from harmful invaders.