A signal is an action that distinguishes one type of person from a would-be mimic because it would be too costly for the mimic to carry out.
信号是区别一类人和一个有意模仿者的行为，因为这个行为代价过高，模仿者很难做到。
2
Using anti-CD3 and anti-CD28 to mimic stimulatory signal I / II, to study their function of activing T cells in order to explore the possible mechanism of immune up and down regulation.