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Thread: Specificity of T-cell reactions

  1. #1 Specificity of T-cell reactions 
    Forum Freshman chicken_boy's Avatar
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    As I understand it, naive t-cells are activated (generally in lymph nodes) by antigens brought by APCs (antigen presentation cells). When the t-cells are activated, they clone and differentiate into effector and memory t-cells that express ligands for E and P selectins, among other things. The endothelial cells at the point of infection express E and P selectins and thus this is how the t-cells home in on their target.

    Now, t-cells are specific to antigens, so different t-cells respond to different antigens. So what happens in the case where you have two infections at two different locations at the same time?

    In both cases, t-cells are activated and endothelial cells at both locations will express E and P selectins. So how do the t-cells specific to the antigens from the infections find the proper target? In other words, let's call the two locations of infection, X and Y. How do the t-cells activated for infection X end up at X and the ones activated for infection Y end up at Y and not vica-versa?

    Thanks.


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  3. #2  
    Forum Professor Zwolver's Avatar
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    just look at it as a before and after the industrial revolution.

    before we had to build wooden carts manually.. but they still transported..
    after we had car's who could travel faster and work with greater efficienty..

    they are like building the factories after the first, and the second they use the factories.

    they won't build cart's manually when they have a factory to produce automobiles :-D

    (or wasn't it what ya meant ?? if not i don't know what you meant )


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    Imagine, being able to create matter out of thin air, and not coming up with using drones for boarding hostile ships. Or using drones to defend your own ship. Heck, using drones to block energy attacks, counterattack or for surveillance. Unless, of course, they are nano-machines in your blood, which is a billion times more complex..
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  4. #3  
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    There are many other signals which direct effector T-cells to their targets, but indeed it is an interesting question. My best guess is that both effector T-cells are transported to the two infection sites. So X and Y arrive at place X; and X and Y will arrive at place Y and will bind the MHCs.
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  5. #4 Re: Specificity of T-cell reactions 
    Forum Cosmic Wizard spuriousmonkey's Avatar
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    Quote Originally Posted by chicken_boy
    How do the t-cells activated for infection X end up at X and the ones activated for infection Y end up at Y and not vica-versa?
    The bloodstream doesn't really care about site x or y. It flows to both.

    That would be my 2 cents.
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  6. #5  
    Forum Masters Degree invert_nexus's Avatar
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    Exactly.
    It's not like there's some sort of red alert put out from a site that says "T-cells needed. Hurry!" and the t-cells come running from their secret headquarters in the heart of the thymus.

    Instead, the t-cells simply circulate at random throughout the body. When they reach an area that is expressing ligands to which they can attach, then they stick. And stick around.
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  7. #6  
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    Quote Originally Posted by invert_nexus
    It's not like there's some sort of red alert put out from a site that says "T-cells needed. Hurry!"
    Yes there is when imflammation occurs chemokines alert the attraction of T-cells to get the infiltration to the infected areas.
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  8. #7  
    Forum Masters Degree invert_nexus's Avatar
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    So. You're saying that when inflammation occurs. Chemokines are sent out giving specific directions to the T-cells to come down route 9. Take exit 11. Don't go past the kidneys, etc...?
    Or...
    The inflammation sends signals to increase production of t-cells (with specific antibodies).
    Which travel at random through the blood stream.
    Arriving at the infection site.
    And doing their job?

    It's a little more complicated than this, of course. With specialized cells traveling to the thymus, lymph node activity, etc... but this is a pretty quicky explanation. It addresses the fact that the t-cells don't take specific routes. As Spuriousmonkey said, they don't care about site X or site Y.
    They just travel with the bloodstream and go where they go.

    This is why, when there's an infection, white blood cell count is up in the entire bloodstream rather than just the route to the infected area.
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  9. #8  
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    Quote Originally Posted by invert_nexus
    It's a little more complicated than this, of course.
    It addresses the fact that the t-cells don't take specific routes.
    Indeed T cells don’t follow specific routes, but without specific red alerts which point out an infection far less T-cells will reach their goals. Hence the definition of chemokine
    chemokine (from The American Heritage® Dictionary of the English Language)
    Any of various cytokines produced in acute and chronic inflammation that mobilize and activate white blood cells.
    If find the comparison with a red alert justified

    Quote Originally Posted by invert_nexus

    This is why, when there's an infection, white blood cell count is up in the entire bloodstream rather than just the route to the infected area.
    at the site of inflammation the white blood cell count will be much higher compared to the random bloodstream level in the infected person.
    This is caused (among others) by the gradient of chemokine released at this site(s)
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  10. #9  
    Forum Cosmic Wizard spuriousmonkey's Avatar
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    My vague memory tells me that chemokines are not discriminate for specific t-cells. Therefore t-cell x would also end up on location y.
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  11. #10  
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    Quote Originally Posted by spuriousmonkey
    My vague memory tells me that chemokines are not discriminate for specific t-cells. Therefore t-cell x would also end up on location y.
    I agree
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  12. #11  
    Forum Masters Degree invert_nexus's Avatar
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    My point was simply that the t-cells don't take specific routes.
    That was the original question, yes?

    However. I can see how you'd mistake my words: "It's not like there's some sort of red alert put out from a site that says "T-cells needed. Hurry!" and the t-cells come running from their secret headquarters in the heart of the thymus."

    The 'red alert' isn't giving directions to the site of infection, rather it is merely putting out a general call for immune cells, yes?
    The cells then go into the bloodstream and go willy-nilly, yes?

    Sure. The area close to the infection will have a higher level of immune cells, but this is because the ligands are available in this area for the immune cells to latch onto. That is, the immune cells go at random until they hit the general area, then they home in on the short term signals...


    Right?
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  13. #12  
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    right
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  14. #13  
    Forum Cosmic Wizard spuriousmonkey's Avatar
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    Quote Originally Posted by invert_nexus
    short term signals...


    Right?
    short range
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  15. #14  
    Forum Masters Degree invert_nexus's Avatar
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    short range
    Semantics...
    Uhm...
    Yeah. That's what I meant. Basically.
    Although, short term might also be applicable?
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