الفهرس 
Toll- like receptorsOnly 14 pages are availabe for public view
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Abstract
TLR are crucial players in the innate immune response to microbial invaders. These receptors are expressed on immune cells, such as monocytes, macrophages, DC, and granulocytes, and at sites of host-pathogen interaction such as airway epithelium and skin. Host cells expressing TLR are capable of recognizing conserved pathogen-associated molecular patterns, and their activation triggers signaling pathways that result in the expression of immune response genes and cytokine production. The patterns of cytokines produced may then instruct the type of adaptive immune response the host will employ to fight the pathogen.
As TLR are instrumental in both launching innate immune responses and influencing adaptive immunity, regulation of TLR expression at sites of disease may be important in the pathophysiology of these diseases. In some cases, as in leprosy, modulation of TLR expression and activation may be protective and lessen the severity of disease. TLR activation, however, may also promote excessive inflammation and apoptosis contributing to the pathology such as the nerve damage seen in leprosy patients. Additionally, the recognition of P.
acnes, a commensal bacterium, through TLR2 induces inflammatorycytokine production that may play a role in the pathogenesis of acne vulgaris.
Thus, TLR are vital players in infectious and inflammatory diseases, making them potential therapeutic targets. Indeed, the ability of TLR to combat disease has already been harnessed through the development of drugs that act as TLR agonists or antagonists. To date synthetic TLR agonists such as imiquimod have found utility in treating viral pathogens and skin cancers, whereas, topical retinoids were found to treat acne vulgaris by downregulation of TLR expression and function.
Therefore, it seems possible that in the future there may be drugs capable of blocking TLR-dependent inflammatory responses, and thus new treatment options for inflammatory diseases such as acne and psoriasis.
The discovery of TLR and the development of drugs that act through them are beginning to have an impact upon our understanding and treatment of several cutaneous diseases, in spite of their importance however, relatively few studies have addressed the role of TLR in skin.
The expression of TLR on keratinocytes and their potential differential expression across the layers of the epidermis is still unclear. Therefore, it seems that additional studies are needed to clarify TLR expression in keratinocytes leaving this promising area of study open for future investigations.