How does protein malnutrition affect the immune system?

• A. Increases immune response
• B. Diminishes immune response
• C. No effect
• D. Improves response to vaccines

Answer: (B)

Protein provides the amino acids needed to make immune cells, antibodies, and the signaling molecules that coordinate defense. When protein intake is insufficient, the body can’t sustain the production and function of these components, leading to a weakened immune system. Lymphocytes and other immune cells decrease in number and activity, antibody levels fall, and phagocytic cells don’t work as effectively. Thymic atrophy and smaller lymphoid tissues reduce adaptive responses, while barriers like the mucosa can become less protective. Altogether, this means a diminished ability to fight infections and a poorer response to vaccines. So, protein malnutrition diminishes immune response.