Which cells in the blood help to protect the body from infection?

White blood cells are the body’s primary defense mechanism against infections. They play a crucial role in the immune system by identifying and attacking pathogens such as bacteria, viruses, and other foreign invaders. There are various types of white blood cells, including neutrophils, lymphocytes, and monocytes, each with specific functions in immune response. For example, lymphocytes produce antibodies that neutralize pathogens, while phagocytes engulf and digest foreign invaders.

The other options do not serve this protective role: red blood cells are primarily responsible for transporting oxygen and carbon dioxide throughout the body, blood platelets are involved in the clotting process to prevent bleeding rather than fighting infections, and plasma cells are a type of white blood cell that specifically produces antibodies but are not responsible for the broader defensive actions against various pathogens. Thus, the pivotal role of white blood cells in combating infections justifies their identification as the defenders within the bloodstream.