Toll-like receptors in viral hepatitis

Toll-like receptors (TLRs) are part of the innate immune system. They recognize some protein, lipid, and nucleic structures that are common in microorganisms such as bacteria and viruses but not present in the human body. The stimulation of TLRs initiates the activation of an intracellular signaling network which results in the secretion of proinflammatory cytokines, mainly type I interferons, TNF-alpha, and IL-6. TLR2, TLR3, TLR4, TLR8, and TLR9 take part in the recognition of viral infections, four of them by discerning nucleic acids, with TLR3 recognizing dsRNA, TLR7 and TLR8-ssRNA, and TLR9-DNA. The role of TLRs in the development of infections and other inflammatory states, neoplasms, and autoimmune disorders is under investigation. The importance of TLRs in the natural course of hepatitis B and C and in the treatment of these diseases are the subject of particular interest. Attempts to apply TLR7 and TLR9 agonists in the treatment of chronic hepatitis type C are underway. A better understanding of the role of TLRs in the complex immunological phenomena accompanying viral hepatitis might put the therapeutic possibilities in these infections into a new perspective.