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Immune Response

by Peter Delves, PhD
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    00:01 We can divide immune responses into innate responses and adaptive responses.

    00:06 And these have particular characteristics.

    00:08 So you may be wondering what the difference is between the innate and adaptive response.

    00:14 Well, I?m going to tell you.

    00:16 Innate immune responses have a very broad specificity for what we call, pathogen-associated molecular patterns, abbreviated to PAMPs; PAMP - pathogen-associated molecular patterns.

    00:32 This is in contrast to the adaptive immune response which has a very high degree of specificity for what we refer to as antigen.

    00:41 Antigen is essentially anything that can be recognized by the adaptive immune response.

    00:47 The innate immune response has the same intensity every single time that the pathogen is encountered.

    00:55 In contrast, the adaptive immune response becomes stronger and faster upon re-infection.

    01:02 We talk about the primary and secondary immune response.

    01:07 This is due to something referred to as immunological memory.

    01:11 And we?ll learn a lot more about immunological memory later on in this lecture series.

    01:19 And then finally, the innate immune response is a rapid response.

    01:25 It occurs within minutes or hours, it?s very quick.

    01:28 And the cells are already present in the body tissues or are recruited directly and very quickly from the blood circulation.

    01:36 So it can happen very, very soon.

    01:39 In contrast, the adaptive immune response is initially rather slow to get going.

    01:45 It takes a few days before it really gets off the ground and is fully effective.

    01:51 And this is because the cells need to proliferate, they need to expand up in number in the secondary lymphoid tissues. So, on the left hand side here, you can see that the innate immune response cells are either already in the tissues. At the bottom there, on the left you can see a tissue macrophage, already sitting in the tissues lying in wait in case an infection comes along. And above that, you can see the multilobed neutrophil cell that is leaving a blood vessel and entering to go to the place where the infection is present in the tissues.

    02:35 In contrast, for the adaptive immune response, you need cell proliferation to occur in the secondary lymphoid tissues. As we?ve already heard, this can take several days to occur fully. And then those cells, once they have proliferated and become activated can leave the secondary lymphoid tissues and then themselves go to the location where the infection is present. So one thing that should already be coming quite clear to you actually, is that the immune system needs to detect that there is a threat. It needs to recognize the enemy.

    03:15 The immune system is there to attack harmful pathogens.

    03:20 A pathogen - something that generates pathology, something that is going to cause disease.

    03:26 So the immune system needs to be able to detect these harmful pathogens.

    03:33 But there are many things that the immune system should not respond to, that we don?t want it to respond to.

    03:39 It does not attack our own healthy body components, what immunologists refer to as ?self?.

    03:49 Also, we?ve already mentioned the beneficial commensal microorganisms or microbiota as they?re often called.

    03:57 These also should not be attacked.

    04:00 Also, food antigens; You probably had something to eat already today.

    04:05 You don?t want to attack the antigens that are present in the food and so forth.

    04:10 So there are many things that the immune system should not attack but there are other things that are harmful that the immune system does need to mount a response against and eliminate from the body.

    04:23 So, how does the immune system actually detect that there?s a threat? Well it has a number of different molecules that we refer to as receptors.

    04:36 And one important immune receptors are the Pattern Recognition Receptors.

    04:42 These are sometimes also referred to as pathogen recognition receptors.

    04:46 I?m afraid as you?ll see, there are many alternative terms that are used in immunology for the same thing.

    04:53 Pattern recognition receptors,pathogen recognition receptors, they both abbreviate to PRR.

    04:59 And they both recognize what are referred to as pathogen-associated molecular patterns or PAMPs, that are molecules that are present either on the surface of pathogens or sometimes inside pathogens.

    05:14 So pattern recognition receptors recognize pathogen-associated molecular patterns in order to determine that there is a threat that needs to be responded to.

    05:28 And the pattern recognition receptor will bind to the pathogen-associated molecular pattern, and this will result in the signal being sent into the cell of the immune system and it will become activated, and begin to mount an immune response.

    05:46 As well as recognizing pathogen-associated molecular patterns or PAMPs, pattern recognition receptors can also recognize damage-associated molecular patterns.

    05:57 So maybe you?re wondering, what?s the difference between a DAMP and a PAMP? Well, a DAMP is something that is produced by our own body.

    06:06 These damage-associated molecular patterns are produced by our own cells when they become damaged, whereas pathogen-associated molecular patterns as the name indicates, are present either on the surface or within pathogens. And just like the pattern recognition receptors bind to pathogen-associated molecular patterns, so they can bind to the damage-associated molecular patterns. In contrast, the cells of the adaptive immune response have antigen-specific receptors. So in general, cells of the innate response have these pattern recognition receptors, whereas the cells of the adaptive immune response have antigen-specific receptors. In actual fact, it?s a little bit more complex than that because we now know that cells of the adaptive response also have pattern recognition receptors, as well as the cells of the innate response. But, the major way in which cells of the adaptive response recognize antigen, is using antigen-specific receptors. And they will bind to the pathogen using these receptors as you can see here.


    About the Lecture

    The lecture Immune Response by Peter Delves, PhD is from the course Immune System: Overview and Cells. It contains the following chapters:

    • The Immune Response
    • How to Recognize the Enemy

    Author of lecture Immune Response

     Peter Delves, PhD

    Peter Delves, PhD


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    clear explanation of immunology
    By Shakira S. on 05. December 2017 for Immune Response

    clear and understandable. covered the main aspects of immunology with simple words and attractive pictures. well done!

     
    Well Explained
    By fatma a. on 13. July 2017 for Immune Response

    no jargons were used. easy to understand and comprehend. Good accent and Highly professional way of conveying the information

     
    thanks
    By Afef J. on 28. March 2017 for Immune Response

    it is made simple, clear and easy to understand regardless the details need to be learned. this is the correct pedagogic way to teach and to learn. This is one of the things that shows that the teacher is a PhD. I wish those lectures were translated in french and that all medical students in my university benefit from it and also every medical student all over the world. Thanks for teaching us and for spreading the knowledge and make things easy for us.

     
    I love the way this doctor explains
    By Hernando J. on 27. February 2017 for Immune Response

    It makes it way easier to understand, I hope he'll guide me though my exam

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