The athymic mouse's immunodeficiency can be classified as what type of disease?

• A. A Secondary immunodeficiency disease
• B. An immune hypersensitivity
• C. A Primary immunodeficiency disease
• D. A Chronic immune complex disease

Answer: (C)

Having no thymus means the mouse cannot properly develop T lymphocytes, so this immune defect is present from birth due to a congenital developmental abnormality. That combination—inherited or congenital immune dysfunction from early life—defines a primary immunodeficiency disease. Secondary immunodeficiencies are acquired after birth from infections, drugs, or malnutrition, which doesn’t apply here. Immune hypersensitivity describes an overactive or misdirected immune response, not a deficiency. Chronic immune complex disease involves ongoing inflammation from immune complex deposition, not a simple lack of immune function. So the athymic mouse is best classified as a primary immunodeficiency disease.