• Question: how does the immune system work?

    Asked by henryjones to Clare, Mariana, Pedro, Robert, Susanne on 16 Nov 2012.
    • Photo: Mariana Campos

      Mariana Campos answered on 16 Nov 2012:

      Hello henry 🙂
      First your immune system has to learn what’s normal: it has to be introduced to each part of your body so that it can learn that is just part of you and should not attack it. Ehen this go wrong and your immune system starts attacking your own body it can lead to bad diseases. After this learning period it attacks pretty much everything that it doesn’t know what it is. There are cells that make holes in bacteria for instance and destroy them.
      It is a really cool system because it can learn. So if you are infected twice by the same bug, in the second time it will respond better and faster. I used to study a bit of this before, with mice.

    • Photo: Susanne Muekusch

      Susanne Muekusch answered on 16 Nov 2012:

      Hi Henry,

      Great that you came back to that! Here is my answer as promised in the chat:

      there are two lines of defense: the innate and the adaptive immunity. Innate immunity does not react to a specific kind of virus or bacteria, but recognises things that are common to a lot of pathogens. It eliminates a lot of pathogens when our body gets in contact with them.

      This innate immunity prevents you from becoming sick quite efficiently: Although the student next to you or sister may have a cold, it does not mean that you will get it, too. you are exposed to the virus, but the components of your innate immune system fight the virus back.

      The innate immune system is evolutionary quite old and even flies have it (-> your part, Mariana 🙂 )

      When the first line of defense, i.e. the innate immunity, fails, the adaptive immunity comes into play. Adaptive means it is specific for every kind of pathogen. It also takes four days until the adaptive immunity has adjusted to a specific pathogen and is working at full speed. Antibodies are produced that bind to the pathogen and mark it for destruction by special cells.

      The adaptive immunity has a memory function: when it has seen a certain pathogen once, it will remember it and react much faster the second time it is exposed to the pathogen. The reaction will be so fast, that you don’t even become sick. That is the principle behind vaccination: We present the adaptive immunity the pathogen, but with an inactivated variant, so it has lost its ability to make you sick. When you come across the real thing, your immune system will remember the pathogen from the vaccination and fight back immediately.

      The immune system is quite a fascinating thing and really complicated with many different cell types and so on. Do you like immunology? I have a friend who is doing a PhD in immunology.

    • Photo: Robert Insall

      Robert Insall answered on 16 Nov 2012:

      Difficult question to answer briefly – lots of people work all their lives on that question.

      You have antibodies in your bloodstream – they remember pathogens and kill any they encounter.

      You also have macrophages – a class of white blood cell – which go around eating anything they think might be an enemy. Google “macrophage” if you want to see some pictures.

      If the macrophages start attacking your joints you get arthritis. Very nasty. Your own immune system attacking your own body.

    • Photo: Clare Taylor

      Clare Taylor answered on 18 Nov 2012:

      Ooh, I love the immune system! I work on bacteria that are very clever and can hide from the immune system or interfere with some of the immune cells like the macrophages that Robert mentions below.

      The two ‘arms’ of the immune system are clever and they communicate with each other to try and get rid of invading bacteria or viruses, or in fact anything foreign that comes into the body. The other scientists have mentioned some important things so I won’t just repeat what they have said! A big difference between the two immune responses is that the innate response takes just minutes and hours to kick in, while the adaptive response is more slow, usually a few days after the infection. The key thing is that the innate system signals to the adaptive system and they work together to fight infections.

      Have you ever heard someone say that their ‘glands are up’ when they are feeling unwell with something like flu or a bad cold? That’s because hundreds of white blood cells travel to little glands called lymph nodes where they try and fight the infectious virus causing the infection. There are so many of them, it causes the lymph node to swell up, and it can sometimes be quite painful. You find these under your neck and by your arm pits so these bits get a bit tender. The swelling is often the first sign that you have an infection!

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