Which system defends against infection and disease?

• A. Immune system
• B. Lymphatic system
• C. Circulatory system
• D. Integumentary system

Answer: (B)

Defense against infection and disease is carried out by the immune system. It includes barriers like skin and mucous membranes, plus specialized cells and molecules such as white blood cells, antibodies, and lymphocytes. The innate immune response acts quickly and generally to many invaders, while the adaptive response targets specific pathogens and builds lasting protection. The lymphatic system supports this defense by transporting immune cells and filtering pathogens through lymph nodes and the spleen, but the primary defender is the immune system. The circulatory system helps move immune cells around the body, and the integumentary system provides the initial barrier, but neither alone is the system that defends against infection and disease.