TLRs or Toll-like receptors, are a family of proteins that are part of the innate immune system. TLRs are transmembranous and recognize pathogen-associated molecular patterns (PAMPs), which are groups of chemical characteristics common to certain types of pathogens. Patterns detected by TLRs include lipopolysaccharide, a compound found on the surfaces of Gram-negative bacteria, and double-stranded RNA, which is an integral part of the life cycles of many viruses. These PAMPs are generally important for the survival of the pathogen, so they are well preserved. Activation of these receptors induces inflammatory responses in leukocytes of myeloid lineage, signaling via NF-κB, which is a transcription factor that activates pro-inflammatory genes. Activated TLRs also increase the production of co-stimulatory molecules such as CD80, CD86 and CD40. These proteins, expressed on the surface of antigen-presenting cells, are necessary for the activation of T-lymphocytes by dentritic cells and macrophages already showing antigens in their MHC type II molecules (Major Histocompatibility Complex, they participate in the presentation of antigens to T lymphocytes)

In addition, TLR-mediated signaling on antigen-presenting cells (APCs) plays an important role in linking the innate and adaptive immune responses.

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2 years ago