The secondary immune response is faster and much stronger than the primary response because
Correct answer: C. memory cells produced in the first exposure are already present in large numbers
- A. the antigen is weaker the second time
- B. the skin has become impermeable to that pathogen
- C. memory cells produced in the first exposure are already present in large numbers
- D. antibodies from the first exposure are still circulating in the same amount
Explanation
A first exposure leaves behind long lived memory B and T cells specific to that antigen, so a second exposure finds a large clone ready to divide and antibody rises within a day or two instead of a week. Antibody from the first response falls to a low level over time, so persistence of antibody is not the main explanation. Vaccination and booster doses work by deliberately creating this memory.
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About Specific Defense Mechanism
Specific defense mechanisms provide targeted immunity through B lymphocytes, T lymphocytes, antibodies and memory cells that recognize particular antigens. Questions cover humoral and cell mediated responses, clonal selection, primary and secondary immune responses, vaccination and passive immunity, while distinguishing adaptive defenses from the immediate, non specific innate response.
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