The self/non-self dualism is still so marked as it was considered for a long time?

For several decades the immune system has been described mainly as a molecular machinery aimed to recognize and eliminate all the non-self molecules or organisms. Actually, recent evidences support the presence of a constant cross talk between the immune system and microorganisms that live within the host as symbionts resulting in the tolerance of non-self bacteria and yeasts. As a whole, the “defensive” role of immunity, described as highly prominent in several contexts of the modern biosciences, should be revised taking into account that the immune system defined during evolution which organisms have to be excluded and killed, and which have to be maintained. These new evidences support the idea that each animal is a dynamic and context-dependent entity with a mixed and tolerant self.