[The role of Toll-like receptors in the pathogenesis of allergic diseases - where is the truth?].

Toll-like receptors (TLRs) are pattern recognition receptors crucial for the innate and adaptive immune response to pathogen-associated molecular patterns (PAMPs). TLR stimulation via microbial products activates antigen-presenting cells, influences the function of T regulatory cells (Treg), determines the Th1/Th2 balance and Th17 cell differentiation, and controls cytokine production in mast cells and activation of eosinophils. The role of TLR receptors in pathogenesis of allergic diseases results from the biological function that they play in activation and regulation of the immune response. However, the exact role still remains a controversial area. Whereas numerous epidemiological studies mainly indicate a protective effect of microbial exposure, experiments show that innate immune stimulation via TLRs may be involved in both development of and protection against allergic diseases. Timing, dose, site and intensity of exposure to environmental factors and host genetic predisposition are clearly crucial to understanding the interaction between innate immune stimulation and allergy development.Furthermore, extensive clinical trials suggest that ligands for TLRs provide new therapeutic targets for protection against and treatment of asthma and allergic rhinitis. The aim of this review is to summarize the current knowledge about the role of TLRs in pathogenesis of allergic diseases. We will further discuss how we can reconcile inconsistencies in the results of existing studies and review information on the potential use of ligands for TLRs in allergy prevention and therapy.