Day 26 (1q41): TLR5, your bacteria detector


Day 26 has 29 protein-coding genes, including TLR5 (Toll-like receptor 5).

When you think of the immune system, you probably think of T-cells, B-cells, and the other alphabet soup of complicated specialized cells of the adaptive immune system, which has a system of learning and remembering about pathogens as you are exposed to them. The adaptive immune system is shared among vertebrates, but we also have a more ancient and primitive immune system (shared with plants) called the innate immune system, which is hardwired to listen for specific threats. The toll-like receptors are part of this ancient immune system. TLR5 specifically detects the flagella of bacteria to mount an inflammatory response.

Toll-like receptors are named after the fruit fly gene toll:

The next step in PRR discovery came from an entirely different line of research. Christiane Nüsslein-Volhard of the Max Planck Institute in Tübingen analyzed mutations in fruit flies. In 1985, she saw a weird-looking fly larva in which the ventral portion of the body was underdeveloped. Her spontaneous comment was “Das war ja toll!” meaning “That was weird!” and she coined the name Toll for the mutated gene. The protein product of the Toll gene was found to cause ventralization, and normal functional activity of Toll is necessary for dorsoventral polarity in the fly. The discovery of Toll was one in a series of discoveries of genes controlling early embryogenesis, which led to a Nobel prize for Nüsslein-Volhard in 1995.

Hannson and Edfeldt, Arterioscler Thromb Vasc Biol. 2005 Jun;25(6):1085-7.

Click here to see your TLR5 gene on Day 26.

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