Pattern Recognition Receptors (PRRs) - Video Tutorials & Practice Problems
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1
concept
Pattern Recognition Receptors
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4m
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In this video, we're going to begin our lesson on pattern recognition receptors or Pr RS. And so, pattern recognition receptors are commonly abbreviated as PR RS. And so these pattern recognition receptors or Pr Rs are really just cell surface receptors of immune cells that are important for sensing and detecting signs of microbial invasion. Now, as we'll learn, moving forward in our course, there are many different types of Pr Rs and these different types of Pr Rs all detect signs of microbial invasion. However, different types of Pr Rs will detect signs of microbial invasion in different areas of the South. And so we'll be able to talk about this as we move forward in our course. Now notice down below, we're showing you our map of the lesson on innate immunity on the left hand side. And notice already in our previous lesson videos, we've talked about the first line defenses and we've also talked about the second line defenses and uh cells of innate immunity. And we've already started talking about the scanning systems that are important for detecting signs of microbes. And so they serve somewhat as security cameras. So we've already talked about cell communication. And now we're focusing on these pattern recognition receptors. Now, moving forward in our course, we're going to talk about several different types of pattern recognition receptors, including toll like receptors or TLRSC type lectin receptors or CLRS, uh nod like receptors or NLRS and rig like receptors or RLRS. And so we'll get to talk about all of these different types of pattern recognition receptors moving forward in our corpse. Now notice that all of these pattern recognition receptors are important for detecting signs of microbial invasion, but they will detect signs of microbial invasion in different areas. And so what we mean by that is that some of the pattern recognition receptors or PR Rs are going to be PR RS found on the cell's surface. And so these Pr Rs found on the cell surface are important for detecting microbial components on the outside of the cell. And so notice that these Pr Rs, these pattern recognition surface receptors that are on the cell surface are important for detecting signs of microbial components and cell damage uh on the outside of the cell. Now, other PR RS are found embedded in the membranes of phagosome and endos themes which are membranes that are brought into the cell um either through the process of endocytosis or phagocytosis. And so notice here we have an endos or phagosome, I might say which is this membrane uh that results from phagocytosis. And uh notice that there are pr Rs here uh embedded in the membrane of the phagosome. And those are going to be important for detecting microbial components that have been ingested by the cell. So some Pr Rs detect components on the outside of the cell. Some pr rs detect components that have been ingested by the cell and then last but not least, some Pr RS are found in the cell's cytoplasm. And so those Pr Rs like this one that you see right here are going to be important for detecting microbial components and damage inside of the cell. So some pr rs detect microbial components outside the cell. Some detect p uh microbial components that have been ingested by the cell and other pr s detect microbial components that are inside of the cell. And so we'll be able to talk about uh these different types of Pr Rs and uh exactly where they are found and what they help detect as we move forward in our course. But for now, this here concludes our brief introduction to pattern recognition receptors or Pr Rs. And once again, as we move forward in our course, we'll get to learn a lot more. So I'll see you all in our next video.
2
concept
MAMPs and DMPs
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In this video, we're going to introduce the two terms MPS and damps. And so first, we need to recall from some of our previous lesson videos that immune cells use pattern recognition receptors or PR RS to detect different types of signs that will indicate either microbial invasion or host cell damage. Now, the term MPS is an abbreviation for microbes associated molecular patterns and microbes associated molecular patterns or MPS is going to represent signs of microbes. Now, signs of pathogens are referred to as PMS and so uh PS are going to be pathogen associated molecular patterns. And so really the terms MPS and PMS can be used interchangeably to refer to a broad group of different types of molecules that are associated directly with microbes or pathogens. And so some examples of MPS or PMS include lipopolysaccharide or LP S A component found in the uh outer surface membranes of uh gram negative bacteria, peptidoglycan, a molecule specific to bacterial cell walls, viral nucleic acids, fungal cell walls and flagella, a protein component important for bacterial flagella. And so these are all direct signs of microbes or pathogens. And so these are all examples of what could be considered MPS or pumps. Now damps on the other hand, are damage associated molecular patterns. And so these are not direct signs of microbes. Instead, they're more like indirect signs of microbes and pathogens, but they are direct signs that indicate host cell damage. And so these are molecules that actually originate from the host, but they indicate host cell damage. So for example, it could be perhaps some kind of phospholipid uh component of a host cell membrane or something of that nature, something that belongs to the host that indicates that the host cells have been damaged. And so if we take a look at our image down below, uh what you'll notice is that this is an image showing you a macrophage uh which is an immune system cell that has many different types of Pr Rs, many different types of pattern recognition receptors. And these different types of Pr Rs can detect either maps or damps in different regions. And so uh some notice that some of these Pr Rs are found on the surface. And so uh these are gonna be capable of detecting microbe or pathogens associated molecular patterns or MPS on the outside of the cells. And so notice here, we're showing you these Pr Rs that are positioned on the cytoplasmic membrane that are gonna be detecting signs of uh microbes outside the cell. And again, uh notice that we have lipopolysaccharide and peptidoglycan and flagellant all being detected by these Pr RS on the outside of the cell. Uh and then uh notice that we have other types of Pr RS that are going to be embedded in the membranes of endo zom or phases. And they can detect maps uh like for example, viral DNA or viral RN A or bacterial DNA uh that have been ingested by the cell. And we have other PR RS that are cytoplasmic Pr Rs that can detect, you know, either MPS or damps and damps are again damage associated molecular patterns, um or just damps and uh those are gonna detect damage to cellular components. And so, uh this here concludes our brief introduction to these terms, MPS and damps, molecular associated uh molecular microbes associated molecular patterns and damage associated molecular patterns. And so we'll be able to apply some of these concepts as we move forward in our course. So I'll see you all in our next video.
3
Problem
Problem
Which of the following are PRRs least likely to detect?
A
Glycolysis enzymes.
B
Peptidoglycan.
C
Flagellin.
D
Lipopolysaccharide.
E
Foreign nucleotide sequences.
4
concept
Toll-Like Receptors (TLRs)
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3m
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In this video, we're going to introduce toll like receptors or TLRS for short. And so, the most well characterized type of PR R or pattern recognition receptor are the toll like receptors. Now, toll like receptors are commonly abbreviated as TLRS. And so these toll like receptors or TLRS are membrane embedded, PR RS or membrane embedded, uh pattern recognition receptors that are used to detect MS um outside of the cell or MPS that have been ingested by the cell through the process of endocytosis or phagocytosis. Now, the TLRS or toll like receptors, once again, they can either be found in the cell membrane uh in the cell cytoplasmic membrane or they could be found embedded in the membranes of endos themes and phagosome, which are these membrane vesicles that result from endocytosis or phagocytosis. Now, the TLRS that are found uh embedded in the cell cytoplasmic membrane will face outward on the cell surface in order to detect uh uh MPS on the outside of the cell. Uh but the TLRS that are found in the endos or phagosome are going to face inward in order to monitor what is engulfed via endocytosis or phagocytosis. And once again, these TLRS are going to recognize MPS such as for example, microbial nucleic acids, like for example, uh double stranded RN A, which is found in some types of viruses but is not common in the host cell at all. And so, once a microbial invasion has been detected, once a map has been detected by a TLR, it can then initiate some kind of immune response, like for example, the release of a cytokine, for example. And so 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 uh which are going to serve to detect signs of microbes and serve somewhat as security cameras. And so these pattern recognition receptors or PR RS are going to help detect signs of MPS and damps microbes associated molecular patterns and damage associated molecular patterns. And 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. And so these toll like receptors or TLRS again are membrane embedded pattern recognition receptors. So they're going to be found embedded in the membrane of the, the cytoplasmic membrane and they will be facing towards the outside of the cell uh where they can detect signs uh like for example, lipopolysaccharide or peptidoglycan or flagella uh or uh they can be found embedded in the membranes of endos or phases and they're gonna be facing inwards so that they can detect what has been ingested uh within the endos or fags. And so uh 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.
5
Problem
Problem
Toll-like receptors (TLRs) bind molecules on pathogens. Why is this helpful to the immune response?
A
It provides a highly specific response to very small and highly unique areas on an individual pathogenic microbe, providing the most specific and selective response possible.
B
It provides a general response to broad categories of molecules/cells that should NOT be in our system, as we don't have these molecules on our own cells.
C
These secreted molecules help bind pathogens and then direct them to receptors on the immune system cells that are best capable of eliminating them from our systems. TLRs are delivery mechanisms for the immune responses.
D
TLRs are capable of directly lysing (destroying) the microbes, helping our immune responses by eliminating pathogens.
6
concept
C-Type Lectin Receptors (CLRs)
Video duration:
2m
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In this video, we're going to introduce the C type lectin receptors or CLRS. And so another type of PR R or pattern recognition receptor that's located on the cell surface are the C type lectin receptors. And so these C type lectin receptors are commonly abbreviated as CLRS. And so these C type lectin receptors or CLRS are again, cell surface pattern recognition receptors or PR RS that bind to car carbohydrate MPS on the microbial surfaces. And so some microbes have carbohydrate uh MPS on their surfaces. And these C type lectin receptors are found on our own immune cells and they can bind to the carbohydrate lamps that are found on these microbial surfaces. Now, lectins themselves, which are found within the name C type lectin receptor are proteins that bind to specific carbohydrates. And so that's really what lectins are. And so if we take a look at our image down below, over here, on the left hand side, once again, we're showing you our map of the lesson on the scanning systems of innate immunity which serve to detect signs of microbes and serve as uh somewhat like security cameras. And so uh here we're talking about the pattern recognition receptors, specifically the C type lectin receptors. And so, uh once again, these C type lectin receptors are going to be membrane embedded receptors on the cell surface. And uh what you'll notice is that uh these C type lectin receptors, they have a green region right here that we refer to as the lectin protein. And the lectin protein is capable of binding to carbohydrates. In fact, it will bind to carbohydrates like this one that are found on the microbial surface. And so uh our host cell is able to use the CLRS to bind and recognize carbohydrate MPS uh found on microbe surfaces. And then once again, uh the C type lectin receptor has bound a uh a carbohydrate map on the microbial cell surface. It can then initiate some kind of immune response, for example, perhaps the release of some kind of cytokine. And so this year concludes our brief lesson on C type lectin receptors or CLRS. And once again, we'll be able to apply some of these concepts as we move forward and learn about the other pattern recognition receptors as well as we move forward to. So see you all in the next video.
7
Problem
Problem
Which of the following is not considered a MAMP (Microbe/Pathogen-Associated Molecular Pattern)?
In this video, we're going to briefly discuss the nucleotide binding and all lier organization domain like receptors or in other words, for short, just the nod like receptors. And so these nod like receptors are commonly abbreviated as NLRS. And unlike the other two types of pattern recognition receptors that we've talked about in our previous lesson videos including the toll like receptors and C type lectin receptors, which are membrane bound receptors. The nod like receptor is not membrane bound. Instead, the nod like receptor or NLR is a cytoplasmic receptor, meaning that it is not embedded in the membrane and it is uh dissolved within the cytoplasm. And so this nod like receptor or NLR is a cytoplasmic receptor protein or a cytoplasmic PR R A cytoplasmic pattern recognition receptor that is going to detect intracellular MPS or damps. So these nod like receptors which are cytoplasmic Pr RS, they play an important role in the immune response of macrophages and dendritic cells. And when an LNLR detects a, a map, uh they can combine with other cytoplasmic proteins to form what is known as an infla zone. And this insome uh can uh be defined as a structure that is capable of activating pro inflammatory cytokine production leading to inflammation. And so if we take a look at our image down below, uh once again, on the left hand side, we have our map of the lesson on the scanning systems. And we're focusing specifically on the nod like receptors here and notice that these knot like receptors can be found in macrophages and dendritic cells and notice that they are cytoplasmic pattern recognition receptors. Ok. So they're found uh dissolved in the cytoplasm. They are not embedded in membranes. And so uh when these nod like receptors, uh or NLRS bind to MPS and damps inside the cell. So here is an NLR binding to some kind of MP or damp. Uh it can lead to uh the formation of what is known as an inflame and the infla moses uh will form which will activate cytokine production. And so here we have the infla uh formation and the formation of the infla masom will uh trigger the release of cytokines. And those cytokines can trigger inflammation and inflammation is an entire response that can help to eliminate the uh microbes that are causing uh problems. And so uh what you can see here is that uh these nod like receptors are again, cytoplasmic pr RS that detect signs of intracellular MPS and damps and can lead to some kind of response that can ultimately help to eliminate those microbes or pathogens. And so this here concludes our brief lesson on the nod like receptors or NLRS. And we'll be able to get some practice applying some of these concepts. And then we'll talk about the final type of pattern recognition receptor, the rig like receptor. So I'll see you all in our next lesson video.
9
Problem
Problem
Why are NOD-like receptors (NLRs) important for macrophage cells?
A
Macrophages commonly ingest infectious material and use NLRs to detect intracellular MAMPs.
B
Macrophages are unstable and commonly have intracellular damage and use NLRs to detect DAMPs.
C
Macrophages use NLRs to detect MAMPs which triggers the formation of RIG-like receptors.
D
Macrophages are the only cells able to detect viral infection and use NLRs to detect viral RNA.
10
concept
Retinoic Acid Inducible Gene (RIG)-Like Receptors
Video duration:
4m
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In this video, we're going to briefly discuss retinoic acid inducible gene like receptors or for short rig like receptors. Now, these rig like receptors are a second type of cytoplasmic PR R in addition to the nod like receptors that we talked about in some of our previous lesson videos. And so once again, these rig like receptors are cytoplasmic Pr RS that are capable of detecting cytoplasmic MPS or cytoplasmic microbe associated molecular patterns. Now, uh specifically these rig like receptors are cytoplasmic proteins or cytoplasmic Pr RS that detect viral RN A. And uh the these uh rig like receptors that are capable of detecting viral RN A in the cytoplasm are found in most types of host cells. Now, the rig like receptors are capable of distinguishing between host cell RN A and viral RN A by two features that we have listed down below. Uh The first feature is that viral RN A can be double stranded and double stranded RN A is quite unique and really only found in some types of viruses and host RN A is not double stranded. So that makes it easy to distinguish the host cells. RN A from viral RN A. Now a second important feature that helps distinguish uh host RN A from viral RN A is that host cell RN A is going to have a five prime calf as well as a poly A tail, uh a three prime polya tail. However, viral RN A does not have a five prime cap or a poly A tail. And so that is another way to distinguish between host cell RN A and viral RN A. And so if we take a look at our image down below, over here on the left hand side, notice we have our map of the lesson on the scanning systems of innate immunity which serve to detect signs of microbes and host cell damage and they serve somewhat as these security cameras. And so here in this video, we're focusing specifically on pattern recognition receptors, uh specifically these rig like receptors. And so uh these rig like receptors uh again, are capable of detecting viral RN A. And so when a virus infects a cell. So here we have an infecting virus, uh it will uncoat and release its genetic material. And that viral genetic material can be transcribed through the process of transcription to make viral RN A, either viral, single stranded RN A or viral, double stranded RN A. And so regardless if it's viral, single stranded RN A or viral double stranded RN A, the uh rig like receptors which are down below right here are capable of distinguishing uh the host cells RN A which notice the host cells, RN A is over here, it is single stranded and it has a five prime cap and a poly tail uh from the viral RN A. And so, uh that's because again, the viral RN A is uh not going to have the five prime cap or poly tail. And also viral RN A can be double stranded. And so these rig like receptors will detect these viral RN A molecules. And upon detecting the viral RN A molecules, it could initiate some kind of immune response. Like for example, the release of a cytokine, perhaps an interferon, for example, which we'll get to talk about the interferon response in more detail later in our course. But for now, this year concludes our brief lesson on these rig like receptors and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.
11
Problem
Problem
What defining features of viral RNA allows the RIG-like receptors to distinguish infecting viral RNA from the host cell’s RNA?
A
Viral RNA has a 5’ cap while host cell RNA does not.
B
Viral RNA has a poly-A tail while host cell RNA does not.
C
Viral RNA can be double stranded while host cell RNA is single stranded.
D
Viral RNA has a circular formation while host cell RNA is linear.
E
None of the above.
12
Problem
Problem
In addition to peptidoglycan, which molecule(s) unique to bacteria would PRRs recognize?
A
Lipopolysaccharide (LPS).
B
Fungal cell walls.
C
Flagellin proteins.
D
Tubulin proteins found in cilia.
E
A and C.
F
B and D.
G
All of the answers would be recognized by PRRs.
13
Problem
Problem
Toll-like receptors are receptor proteins on ___________.
A
Granulocytes that destroy parasitic helminths.
B
Phagocytes that recognize foreign or microbe-associated molecules.
C
Viruses entering the body which stimulate the immune system.
D
Mucus producing cells that trigger mucus production when they bind with an allergen.
14
Problem
Problem
Which type of pattern recognition receptor when bound to MAMPs triggers the formation of the inflammasome?
A
NOD-Like Receptors.
B
RIG-Like Receptors.
C
Toll-Like Receptors.
D
C-Type Lectin Receptors.
15
Problem
Problem
Toll-like receptors:
A
Are cytokines.
B
Each recognize a specific "danger" molecule.
C
Are embedded in cellular membranes.
D
Are part of adaptive immunity.
E
b and c.
16
Problem
Problem
______ on phagocytes bind to PAMPs on bacteria, triggering uptake & destruction of the bacterial pathogens?
A
PRRs.
B
PAMPs.
C
AMPs.
D
PMNs.
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