Innate and adaptive immunity: specificities and signaling hierarchies revisited

The conventional classification of known immune responses by specificity may need re-evaluation. The immune system can be classified into two subsystems: the innate and adaptive immune systems. In general, innate immunity is considered a nonspecific response, whereas the adaptive immune system is thought of as being very specific. In addition, the antigen receptors of the adaptive immune response are commonly viewed as 'master sensors' whose engagement dictates lymphocyte function. Here we propose that these ideas do not genuinely reflect the organization of immune responses and that they bias our view of immunity as well as our teaching of immunology. Indeed, the level of specificity and mode of signaling integration used by the main cellular participants in the adaptive and innate immune systems are more similar than previously appreciated.