But measuring " memory" T cells is much more difficult.

但测量" 记忆" T细胞要困难得多。

Over time, as the invading pathogen dies off, most of the B and T cells die of neglect, but a few turn into memory B cells and memory T cells, which linger for years in case they're needed in the future.

时间不断推移，随着入侵病原体的死亡，大多数B细胞和T细胞会因闲置而死亡，但一小部分会转变成记忆B细胞和记忆T细胞；它们会逗留多年，以备不时之需。