What is the impact of immunodeficiencies on infection risk?

• A. Impaired immunity increases the risk for infections
• B. Impaired immunity decreases infection risk
• C. No effect on infection risk
• D. Increases risk only for viral infections

Answer: (A)

Immunodeficiencies raise infection risk because the immune system cannot mount effective defenses against invading pathogens. The body relies on both innate and adaptive immunity to recognize and clear infections: innate defenses like neutrophils, macrophages, and complement act quickly to stop pathogens, while adaptive defenses—antibodies from B cells and targeted T-cell responses—provide specific, long-lasting protection. When any part of this system is deficient, pathogens can invade more easily, persist longer, and cause more frequent or severe infections.

The exact pattern of infections depends on which component is affected. For example, antibody deficiencies tend to cause recurrent bacterial infections, especially with encapsulated bacteria, and may lead to more sinus and lung infections. T-cell defects predispose to viral, fungal, and intracellular infections. Neutrophil or phagocyte defects raise risk for bacterial and fungal infections, while certain complement deficiencies increase susceptibility to encapsulated bacteria. Across the board, immunodeficiency leads to increased susceptibility, not a decreased risk, not no effect, and not limited only to viral infections.