When microbes were first recognized as the cause of infectious diseases, it was immediately clear that multicellular organisms must be capable of recognizing them when infected and, hence, capable of recognizing molecules unique to microbes.
Cando se descubriu que os microbios eran a causa das doenzas infecciosas, fíxose evidente que os organismos pluricelulares tiñan que poder recoñecelos cando eran infectados e, por tanto, tiñan que poder recoñecer as moléculas microbianas.