ABSTRACT
Classical immune memory is thought to be possessed by adaptive immune system.It is featured by a specific memory of previous exposure to microbes and enhanced responses to reinfection accordingly in adaptive immune cells.Traditionally, it is believed that innate immunity does not have such characteristics.However, recent researches have raised doubts regarding this view.Studies have found that in mammals and other organisms that lack adaptive immunity, the innate immune system can change the manner and intensity of response to the second infection by certain pathogens, which is a phenomenon referred to innate immune memory.Unlike the antigenic receptor gene rearrangement to produce memory in adaptive immune cells, the training immunity in innate immune cells is mediated by epigenetic reprogramming.Innate immune memory does not always protect the body against infection or stress.It also results in toleranced immunity, which leads to a lowered immune response to pathogens infection and participates in the development of a variety of infectious diseases.Therefore, a tight regulation of innate immune memory may be critical for the therapy of refractory infections caused by sepsis-induced immune paralysis.