Toll-like receptor 1

Toll-like receptors (TLR) belong to the group of PRRs (Pattern Recognition Receptors), which are used for the recognition of so-called "Pathogen Associated Molecular Patterns" ( PAMPs ). TLRs are mostly found on or in pathogens and control the activation of certain genes. There are now 10 (TLR-1 to 10) and 12 murine (TLR-1 to 9 + 11 and 13) in humans. 6 of the human TLRs bind PAMPs extracellularly (TLR-1, 2, 4, 5, 6, 10) while 4 are only localized intracellularly (TLR-3, 7, 8 and 9).

TLRs are expressed by immune cells of the innate and also by cells of the adaptive immune system (B and T cells). This wide distribution makes TLRs an excellent tool for both the innate and the adaptive immune system. TLRs are thus responsible for the recognition of pathogens and the activation of antigen-specific acquired immunity. Through the activity of TLRs, the innate defence mechanisms (see below immunity, innate) can distinguish between "self" and "foreign".

TLR1 is a coreceptor for TLR2 and is located on the cell surface. The TLR1/TLR2 dimer recognizes MAPMs on the cell surface like tri-acetylated microbial lipoproteins (MAMP=microbial associated molecular pattern).

Polymorphisms in the genes encoding TLR1, TLR2, TLR4, TLR6 lead to a number of diseases. The "TLR1 G1805T" polymorphism in the TLR1 gene is associated with an increased risk of tuberculosis for Africans and American Hispanics (Zangh et al. 2013). In contrast, the WG genotype "TLR1 rs4833095" is associated with a lower susceptibility to tuberculosis infection.

Possibly TLR1/TLR2-dimers play a modulating role in the pathogenesis of acne vulgaris. The toll-like receptor TLR2 and various The Toll-like receptor TLR2 and various polymorphisms have important effects in various autoimmune diseases; the co-function of its dimer TLR1 is not always clear.

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5. Zhang Y et al(2013) Toll-like receptor -1, -2, and -6 polymorphisms and pulmonary tuberculosis susceptibility: a systematic review and meta-analysis. PLoS One 8:e63357.