Toll receptors belong to the family of receptors with a high evolutionary conservatism . They play an important role in the activation of insect resistance until wrodzonejod birds. For the first time been detected and characterized in Drosophila ( Drosophila melanogaster ) , where they are involved in embryogenesis and immunity against pathogens . We detected a homologous receptors in a mammal, including a human, which is called Toll -like receptors ( TLRs , Toll -Like Receptors ) . Just as in Drosophila , mammalian TLRs include the extracellular domain portion of many repeats of leucine ( LRR , Leucine Rich Repeats ) , a transmembrane domain , and a cytoplasmic domain homologous to the cytoplasmic domain of the type I receptor of interleukin 1 (IL- 1RI ) . TLRs are predominantly on monocytes, macrophages , granulocytes , but also on lymphocytes , epithelial cells and endothelium . There are also known soluble forms of these receptors found in secretory fluids . Currently known types of human TLRs 10 . Are also partially understood their ligands that are derived mainly from microorganisms ( acids) , but also on the host ( endogenous ) . TLRs recognize , in the case of exogenous ligands , so-called . molecular patterns associated with pathogens ( PAMPs ; Pathogen Associated Molecular Patterns ) , and endogenous ligands for these proteins are generated during cell and tissue damage . Connection to the TLR ligand causes rapid activation of innate immunity , inflammation initiated by induction of proinflammatory cytokine production , increased expression of antigens of the major histocompatibility complex class I and class II , costimulatory molecules on antigen presenting cells (APC , Antigen Presenting Cells ) , and as a goes better antigen presentation and, consequently, the corresponding activation of adaptive immunity . Detailed knowledge of effector mechanisms and signal transduction by ligand binding to TLRs may be important in understanding mechanisms of recognition or foe , activation of the inflammatory process and the importance of innate immunity for activation , specificity and type of acquired immunity .