Toll-like receptor 1

Toll-like receptors (TLR) belong to the group of PRRs (Pattern Recognition Receptors), which serve to recognize so-called "Pathogen Associated Molecular Patterns" (PAMPs). TLRs are usually 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) TLRs in humans. 6 of the human TLRs bind PAMPs extracellularly (TLR-1, 2, 4, 5, 6, 10) while 4 are exclusively 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 the innate and the acquired immune system. TLRs are thus responsible for the recognition of pathogens and the activation of antigen-specific acquired immunity. The activity of TLRs enables the innate defense mechanisms (see below Immunity, innate) to differentiate between "self" and "foreign".

TLR1 is a co-receptor for TLR2 and is localized on the cell surface. The TLR1/TLR2 dimer recognizes MAPMs such as tri-acetylated microbial lipoproteins (MAMP=microbial associated molecular pattern) on the cell surface.

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 developing tuberculosis in Africans and American Hispanics (Zangh et al. 2013). In contrast, the AG genotype "TLR1 rs4833095" is associated with a lower susceptibility to tuberculosis infection.

It is possible that TLR1/TLR2 dimers play a modulating role in the pathogenesis of acne vulgaris. The Toll-like receptor TLR2 and various polymorphisms have significant effects in acne vulgaris. polymorphisms have significant 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.