Why does a second exposure to a pathogen produce a faster and stronger immune response than the first?
Answer and explanation
Correct answer: D. Memory cells were formed during the first exposure
- Step 1: B and T cells that recognized the pathogen produce long-lived memory cells. Step 2. They respond quickly on the next exposure. Answer: memory cells. Why not the others: Active cytotoxic T cell destruction acts on infected cells rather than circulating pathogens, and maternal IgG placental transfer provides temporary passive immunity rather than an enduring adaptive secondary memory response.
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