When they receive the signal they make - they change in a very specific way and the cell can recognize this change that's occurred at the cell surface.

当它们接收到信号之后,就会发生十分特殊的变化,细胞能够识别自身表面发生的这种变化

耶鲁公开课 - 生物医学工程探索课程节选

Another subset of T-cells called T helper cells will recognize that signal by direct contact with it, and they will become activated and proliferate.

另外一个T细胞的亚群是辅助性T细胞,辅助性T细胞可识别与其接触的抗原信号,并被激活,开始增殖

耶鲁公开课 - 生物医学工程探索课程节选