Why is the tritiated thymidine pulse typically added only during the final 18–24 hours of a 5–6 day LST culture rather than at the beginning?
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A
To capture peak S-phase activity without saturating the cells or depleting the label during early low-level proliferation
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B
To reduce radiation exposure to laboratory personnel during the culture period
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C
Because thymidine inhibits antigen presentation when present from day 0
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D
To allow cytokine production to occur before DNA synthesis is measured