Which liquid is part of the lymphatic system and helps fight infections?

• A. Plasma
• B. Platelets
• C. Lymph
• D. Serum

Answer: (C)

Lymph is the fluid of the lymphatic system and plays a key role in immune defense. It forms from interstitial fluid that drains from tissues into lymphatic capillaries, then travels through a network of vessels to lymph nodes where immune cells monitor for pathogens. Lymph carries lymphocytes and other immune cells, plus antigens, enabling the body to detect and respond to infections as immune reactions are triggered. This is why it’s considered part of the lymphatic system and directly involved in fighting infections. By contrast, plasma is the liquid component of blood, serum is plasma without clotting factors, and platelets are cell fragments involved in clotting rather than a lymphatic immune fluid.