What happens to the majority of B and T cells activated during the primary immune response after the perceived threat passes?

Answer

Most of the activated cells die off.

After the initial battle against the perceived invasion is won, most of the rapidly proliferating B and T cells that fought the threat undergo apoptosis, leaving behind only a small, specialized reserve group.

What happens to the majority of B and T cells activated during the primary immune response after the perceived threat passes?
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