The toll-like receptors are innate immunity receptors which recognise particular exogenous structures in the microorganisms pathogen associated molecular pattern (PAMP) and endogenous structures damage-associated molecular patterns (DAMP). Eleven TLR have been identified among human beings. These are danger receptors located in the cells of the immune system but also in other cells. Their primary function is the recognition of pathogens and the activation of the cell that holds them. It follows from it an action on the cells environment, inflammation cells and an activation of the adaptive immunity. The knowledge of the intracellular signalisation ways of the TLR has allowed us to understand the physiopathology of certain diseases. Thus, several works use the agonists of TLR to stimulate them: vaccines against infectious diseases, allergies and cancers. The antagonists are used to block the TLR in autoimmune and chronic inflammatory diseases. It is clear that the border between innate and adaptive immunity fades and that these two components of the immune response are closely related, thus opening up new prospects diagnostic and therapeutic procedures.