In this video, we're going to introduce Toll like receptors or TLRs for short. The most well-characterized type of PRR, or pattern recognition receptor, is the Toll like receptors. Now, Toll like receptors are commonly abbreviated as TLRs, and these Toll like receptors or TLRs are membrane-embedded PRRs or membrane-embedded pattern recognition receptors that are used to detect MAMPs outside of the cell or MAMPs that have been ingested by the cell through the process of endocytosis or phagocytosis.
The TLRs or Toll like receptors can either be found in the cell membrane, in the cell cytoplasmic membrane, or they could be found embedded in the membranes of endosomes and phagosomes, which are these membrane vesicles that result from endocytosis or phagocytosis. The TLRs that are found embedded in the cell's cytoplasmic membrane will face outward on the cell surface in order to detect MAMPs on the outside of the cell. But the TLRs that are found in the endosomes or phagosomes are going to face inward in order to monitor what is engulfed via endocytosis or phagocytosis.
Again, these TLRs are going to recognize MAMPs, such as, for example, microbial nucleic acids. Like, for example, double stranded RNA, which is found in some types of viruses but is not common in the host cell at all. Once a microbial invasion has been detected, once a MAMP has been detected by a TLR, it can then initiate some kind of immune response, such as the release of a cytokine, for example.
If we take a look at our image down below over here on the left-hand side, notice that we're showing you our map of the lesson on the scanning systems of innate immunity, which are going to serve to detect signs of microbes and serve somewhat as security cameras. These pattern recognition receptors or PRRs are going to help detect signs of MAMPs and DAMPs, microbe-associated molecular patterns and damage-associated molecular patterns.
There are many different types of pattern recognition receptors, but here in this video, we're focusing on the Toll like receptors or the TLRs. Again, these Toll like receptors or TLRs are membrane-embedded pattern recognition receptors. They're going to be found embedded in the membrane of the cytoplasmic membrane, and they will be facing towards the outside of the cell, where they can detect signs, like, for example, lipopolysaccharide, peptidoglycan, or flagellin, or they can be found embedded in the membranes of endosomes or phagosomes, and they're going to be facing inwards so that they can detect what has been ingested within the endosome or phagosome.
This here concludes our brief lesson on these Toll like receptors or TLRs, and we'll be able to learn about the other types of pattern recognition receptors as we move forward in our course. So I'll see you all in our next video.