Which cells in the body are responsible for defending against foreign invaders?

White blood cells, also known as leukocytes, play a critical role in the immune system by defending the body against foreign invaders such as bacteria, viruses, and other pathogens. They are essential for identifying and targeting these threats, initiating appropriate immune responses, and facilitating the destruction of harmful microorganisms.

Unlike red blood cells, which are primarily responsible for carrying oxygen to tissues and removing carbon dioxide, or platelets, which are crucial for blood clotting and wound healing, white blood cells are specifically designed to recognize and combat infections and foreign substances. They can be further categorized into different types, such as neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with unique functions in the immune response.

Plasma cells, meanwhile, are a type of white blood cell that specifically produces antibodies against antigens. However, they fall under the broader category of white blood cells and do not represent the entire immune defense. In summary, the primary role of white blood cells encompasses the defense against pathogens, which distinctly sets them apart as the main cells involved in the body's immune response.