La notion de danger

Immunologists have traditionally focused on the adaptive immune response, and have considered that its main function is to distinguish between self (endogenous) and non-self (foreign) antigens. In contrasts, a number of researchers have recently proposed that the main function of the immune system is to eliminate microbial pathogens. The innate immune system, largely neglected in the past, plays an essential role in initiating anti-microbial responses. This system reacts rapidly against infections, and in parallel, it activates and influences the adaptive systems. Several theories have been proposed to explain how the innate and adaptive immune response and affect immune tolerance. According to the model of << immune danger >>, any agent capable of destroying tissue through necrosis and inflammation can trigger an immune response. The << danger model >> has recently converged with a second one, which proposes that the innate system recognizes microorganisms mainly through specific structural motifs expressed by pathogens but not by the host. In contrast, a competing model claims that activation of the immune system is determined by the location and the dose of the antigen, and by the duration of antigen exposure. All three models often invoke microbial pathogens (known or still unknown) to account for autoimmune pathologies.