Explain the difference between primary and secondary immunodeficiencies with an example of each.

• A. Primary immunodeficiencies are genetic defects; secondary immunodeficiencies are acquired (e.g., HIV infection, chemotherapy)
• B. Primary immunodeficiencies are acquired; secondary are genetic
• C. Primary immunodeficiencies are caused by infections
• D. Secondary immunodeficiencies occur only in infancy

Answer: (A)

The main idea is origin: primary immunodeficiencies come from inherited genetic defects that affect how the immune system develops or functions, and they are usually present from birth. Secondary immunodeficiencies are acquired after birth due to external factors that weaken immunity, such as infections or treatments.

An example of a primary immunodeficiency is severe combined immunodeficiency (SCID), which results from mutations in genes needed for the development and function of T and B cells, leading to severely impaired adaptive immunity.

An example of a secondary immunodeficiency is HIV infection, which destroys CD4 T cells and weakens the immune response, or chemotherapy, which can impair bone marrow function and reduce immune cells.

So, the best description emphasizes that primary immunodeficiencies are genetic defects present from birth, while secondary immunodeficiencies are acquired due to external factors like infections or treatments.