Which type of cells is primarily responsible for fighting infections in the body?

White blood cells, or leukocytes, are the primary cells responsible for fighting infections in the body. They play a crucial role in the immune system, protecting the body against pathogens such as bacteria, viruses, and other foreign invaders. White blood cells are equipped with various mechanisms to identify, target, and eliminate these harmful organisms.

Different types of white blood cells serve specific functions; for example, neutrophils and macrophages engulf and destroy pathogens through a process called phagocytosis, while lymphocytes are involved in producing antibodies and coordinating the immune response. This diverse functionality allows white blood cells to respond effectively to a wide variety of infections.

In contrast, red blood cells are primarily responsible for transporting oxygen from the lungs to the tissues and carrying carbon dioxide back to the lungs, while platelets are essential for blood clotting. Stem cells have the potential to develop into various types of cells but do not directly fight infections themselves. Therefore, white blood cells are the correct answer as they are specifically designed and trained to tackle infections in the body.