B and T cells make up the adaptive immune system, while NK cells are part of the innate immune system.

B细胞和T细胞组成了适应性免疫系统，而NK细胞是固有免疫系统的一部分。

There are always exceptions to this rule, but in general, if you see " b" and " t" , usually you do not pronounce the " b" .

这个规则总是有例外， 但一般来说，如果你看到“b” 和“t” ，通常你不会发音“b” 。

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。