Review of the Complement System - Video Tutorials & Practice Problems
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Review of the Complement System
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In this video, we're going to do a review of the compliment system. And so because this video is a review, what that means is that there's really no new information here in this video. And so if you're already feeling really good about the compliment system, then you can feel free to skip this video. But if you're looking for a good way to review a lot of the concepts that we talked about in our previous lesson videos, then stick around because this might be a really helpful review for you. And so in reviewing the complement system, we're going to review the activation pathways as well as the responses or the effects of activation of the complement system. And so recall that the complement system consists of inactive proteins that are circulating in our blood and circulating through the tissues. And so these inactive complement system proteins can become activated by one of three different pathways, the alternative pathway, the lectin pathway or the classical pathway. Now, the alternative pathway will activate the complement system uh and is triggered by C three B A complement system fragment, binding to the surface of invading microbes. And when C three B binds to the surface of invading microbes. It helps to activate the complement system. And uh of course, the alternative pathway is going to ultimately lead to the formation of the enzyme C three converse, which is actually um where all three of these pathways converge together. So the lectin pathway is going to be triggered and activate the complement system through the MBL, the mannose binding lectin. And so the mannose binding lectin consists of a protein that binds to nanos carbohydrates that are found on the surface of microbes. So they bind to the surface of invading microbes by binding to the Manno on those microbes. So here in this image, notice that the manos is represented by these little green hexagons that are on the surface of the microbe. And the lectin, the manos binding lectin or the MBL is represented by this structure that you see here. And so when the manno's binding lectin binds to the nanos on the surface of the microbes, it will lead to a cascade of events that ultimately leads to the formation of C three converse. And then the classical pathway is going to be triggered and activate the complement system. When antibodies from the adaptive immune system are going to bind to antigens on the surface of microbes. And ultimately, these antibodies from the adaptive immune system that bind to the surface of these microbes leads to a cascade of events that once again leads to the formation of C three converse. And this classical pathway here has an asterisk next to it because the classical pathway is um really why the complement system is called the complement system. Because through the classical pathway, the complement system, which is part of innate immunity is able to complement the adaptive immunity. And that's because the antibodies are part of adaptive immunity and the antibodies help to trigger the complement system, which is part of innate immunity. So there's some cross talk between innate immunity and adaptive immunity right here through the classical pathway. But regardless of which pathway is used, the alternative lectin or classical pathway, they all lead to the formation of C three converse which is an enzyme that is being represented as scissors here because this enzyme C three converse will cleave or fragment this inactive complement system protein called C three. And when C three is cleaved by C three converse, it will be cleaved into C three A which is over here as well as C three B which is over here. And so there will be high levels of C three A and high levels of C three B after the formation of C three converse. Now the C three A along with other complement system proteins such as for example, C five A can go on to trigger the inflammatory response to uh help eliminate microbes. And C three B can go on to act as an ox to allow for oxidization, which is going to improve the effectiveness of phagocytosis, allowing phagocytes like macrophages to phagocytose microbes much easier and much more effectively. And C three B can also interact with a series of other complement system proteins to lead to microbe cell lysis through the formation of membrane attack complexes that form pores in the membranes of gram negative bacteria such as uh these uh bacterial that's being shown here. And so this year concludes our review of the complement system and we'll be able to apply some of the concepts that are in this review as we move forward. So I'll see you all in our next video.
2
Problem
Problem
Which of the following statements about the complement system is true?
A
There are many methods of triggering the complement system.
B
There are many immune responses triggered by the complement system.
C
All triggers of the complement system lead to the formation of C3 convertase.
D
C3a and C3b result in different immune response for the complement system.
E
All of the above are true.
3
Problem
Problem
Which complement molecule is an attractant for neutrophils?
A
C4b.
B
C5a.
C
C3b.
D
C7a.
4
Problem
Problem
The key molecule upon which all complement pathways converge is
A
C1.
B
C2.
C
C3.
D
C6.
5
Problem
Problem
The complex resulting from complement activity that leads to cell lysis is the
A
Prostaglandin complex.
B
Leukotriene activating complex.
C
Membrane attack complex.
D
Histamine complex.
6
Problem
Problem
Which of the following are most susceptible to complement lysis?
A
Gram-positive bacteria.
B
Gram-negative bacteria.
C
Bacteriophages.
D
Prions.
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