Which of these is primarily responsible for protecting the body from infections?

The immune system is primarily responsible for protecting the body from infections. It is composed of various cells, tissues, and organs that work together to identify and eliminate pathogens such as bacteria, viruses, fungi, and parasites. Key components of the immune system include white blood cells, antibodies, and the lymphatic system, which all play essential roles in detecting foreign invaders and mounting an appropriate response to them.

While other systems contribute to overall health and can have roles in defense, such as the cardiovascular system delivering immune cells throughout the body, the primary function of the immune system is specifically focused on identifying and neutralizing threats to health. The nervous system is primarily involved in transmitting signals and processing information, while the respiratory system is responsible for gas exchange and does have some role in immune defense (e.g., mucous membranes that trap pathogens), it does not have the central role that the immune system does in combating infections.