Free Microbiology, Disease, Immunity and Public Health Quiz | University Admission Biology Practice

Microbiology, Disease, Immunity, and Public Health

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A person was injected with a harmless preparation of antigen X on day 0 and again on day 30. The concentration of antibody against X in the blood was measured. Note that the vertical axis is logarithmic.

Which option best explains why the response after the second injection is faster and greater, and correctly names the type of immunity produced?

Select one option.

The second dose contained ready-made antibodies against X; artificial passive immunity
Memory B cells formed during the first response divide rapidly into plasma cells on second exposure; artificial passive immunity
Phagocytes learned to recognise X and produced antibodies directly; natural active immunity
Antibodies from the first injection remained in the blood and multiplied; artificial active immunity
Memory B cells formed during the first response divide rapidly into plasma cells on second exposure; artificial active immunity

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