Which factor is an example of immunity-affecting determinants?

• A. Previous exposure/natural infection
• B. Weather
• C. Climate change
• D. Noise

Answer: (A)

This item is testing how immune status can be shaped by a person’s prior experience with pathogens. When someone encounters a pathogen and develops natural infection, the body builds adaptive immune memory—memory B cells and T cells, plus antibodies—that recognize that pathogen in the future. On subsequent exposures, the immune system can respond quickly and strongly, often preventing infection or reducing disease severity. That direct change in the body's immune readiness is what makes previous exposure or natural infection an immunity-affecting determinant.

Weather and climate change influence how likely someone is to encounter pathogens by altering transmission and environmental conditions, but they don’t directly modify the immune system itself. Noise is unrelated to immune defenses in the way this concept uses, so it doesn’t reflect an immunity-affecting determinant.