摘要
The evolution of mechanisms to fight pathogens in plants and animals is reflected in the complexity of the components of their so-called immune systems. Higher vertebrates have
The evolution of mechanisms to fight pathogens in plants and animals is reflected in the complexity of the compo- nents of their so-called immune systems. Higher vertebrates have evolved two different ways to protect themselves against infectious pathogens [1]. The first is termed innate immunity and is mediated by non-clonatly distributed re- ceptors, which can also be found in plants with less com- plexity, while the second is termed adaptive immunity using clonally distributed receptors. It is thought that adaptive immunity is evolutionarily conserved and is present in or- ganisms from early evolutionary periods, such as the am- phioxus [2-4]. Because of the diversity of clonally distrib- uted receptors, including T cell receptors and immunoglob- ulins, the adaptive immune system is capable of the precise recognition of almost all biological structures. In contrast, the innate immune system is mediated by pattern recogni- tion receptors, such as Toll-like receptors （TLR）,
