Final answer:
White blood cells fight infection in the arm, chest, and neck regions by destroying pathogens through phagocytosis.
Step-by-step explanation:
The component of the body that fights infection in the arm, chest, and neck regions are white blood cells. White blood cells are part of the body's immune system and protect against pathogens, microorganisms, and other harmful substances. Specifically, a type of white blood cell called phagocytes, such as neutrophils, travel to areas of inflammation and destroy pathogens through a process called phagocytosis.