You have just come home from holiday and what a brilliant time you have had. But you were away for four weeks and had eaten all your provisions before you left. The washing is now in the machine and various bits of holiday paraphernalia are scattered all over the living room floor as you decide where you are going to put the extremely expensive crystal that you brought back.
The doorbell goes and a friend has popped by, bringing her 2 year old child with her. Normally their visit wouldn’t be a problem, but you don’t want your glassware damaged by a curious toddler. You invite them in and then rush around, frantically trying to tidy up the floor and put your holiday purchases out of harm’s way. (You might even try to whip up a snack from the nothingness in your cupboards!) Had you known they were coming though, there would have been no crystal on the floor and possibly a packet of biscuits in the cupboard.
Knowing things in advance allows us to prepare for them. It also saves us rushing around trying to do something with far too little time. Planning is key to running our lives efficiently.
Your body is no different. It likes routine and structure, and when it comes to infectious diseases, a bit of forward planning goes a long way.
Hi, Alina here. Me and my friends and cousins make the instructions for your body. We also make them for every other living thing out there. We call ourselves the Dinky Amigos, but you might know us as DNA.
Today I am in a cell called a T cell. These cells form part of your immune system, helping to keep you fit and healthy. We are generally really quick to respond to reports of invaders. But sometimes we need to be prepared first.
This is really important if you ever come into contact with a disease called measles.
Measles is caused by a virus called MeV. It is one of the rudest viruses we know. MeV hides in droplets of other people’s mucus. When they cough, you can breathe them in. The viruses then travel to your lungs and sneak into the cells there. Like all viruses, they use your own cells to make copies of themselves before bursting your cells open and rushing off to find more. If this happens to enough cells, you will get poorly. If it happens to too many cells, you could die. So it’s really important we put a stop to it.
Sneaking under the Radar
Some of the cells that MeV infects are also part of your immune system. These immune cells have been instructed to flag up any intruders in the body. They know to send a distress signal. Our T cells can then come rushing in and sort them out. But MeV knows this and stops them from sending their warning. Our T cells don’t even realise these viruses have got into your body.
The poor immune cells get really distressed and send out other signals. These signals aren’t normally used to tell us about invaders and we don’t realise anything is wrong. Until it is too late.
We are normally really effective at stopping an attack. But only when we know about it.
By the time we find out, there is a big problem.
Is it too late?
It might be.
By the time we find out, the viruses has been in your body for at least five days. Sometimes as long as 10 days. They have travelled from the lungs all over your body, causing damage wherever they go. There are burst cells and copies of MeV everywhere. We only notice when they start trying to infect the T cells.
What cheek! Trying to attack our very defences.
Well, they’ve chosen to attack the wrong cells and we spring into action immediately.
Armies of T cells and other immune cells are needed to bring the virus back under control. It can take anything from two days to two weeks to get a grip on the chaos. All the while you might be feeling really poorly.
Even though you may be ill, we have to give instructions to squirt special chemicals in some of your other cells to stop the virus spreading. This turns your skin a red, blotchy colour and makes you itch. Sorry about that but it’s the only way to stop them.
After we have stopped them and you are no longer ill, it takes us months to clear up and get rid of the virus from your body.
But at least you aren’t ill anymore…
You see, while we are busy with the measles virus, we don’t always have time to patrol your body and deal with any other invaders. So if someone else coughs all over you, the neighbour’s dog decides to slobber all over you or you forget to wash your hands after going to the toilet, you could get infected by something else. Then we have to start fighting off that invader whilst trying to get rid of the measles virus at the same time. This doesn’t always work. Especially in small children or people with weakened immune systems. This time you might be even more ill. Or die.
Luckily, after clearing your body of an MeV infection, we remember what these viruses look like – oh boy do we remember – and you will never get infected by them again. Ever.
Getting ahead of the measles game
What a palaver. That’s how we used to do It in the olden days, and loads of people died. We just couldn’t keep up. Now we have scientists and they have done a brilliant job in developing a vaccine for this horrible virus.
Vaccines are great. They act like little photos so we know what to look out for should you ever be the target for one of these little invaders. Then we can react a lot more quickly.
If your Mum had measles, she will have passed one of these photos on to you with her breast milk. We can use them for about a year, but then they fade too much for us to see them. After that we are on our own. We don’t want you to actually get the measles. It is far too much work and we might not be able to help you.
It’s much easier to get vaccinated. Then we get to play the measles virus at its own game.
Making an MeV vaccine
Scientists (because they are a lot bigger than us) can take the virus and make it infect chicken cells. They only infect cells in a dish; not live chickens. That would be mean.
MeV thinks it’s all clever and gets the chicken cells to help it make loads of copies of itself. Then all the copies burst out the cell and find more chicken cells to infect. The scientists make sure that it infects hundreds of cells. MeV thinks it’s amazing and gets really, really good at infecting chicken cells. So good in fact, that it forgets how to infect any other cells including yours. What an idiot!
Those rubbish copies of MeV can then be put in the measles vaccine for humans.
Once injected into human cells, they haven’t a clue what to do! They can’t infect you and make you ill. But our T cell can find them and, before we destroy them, we can get all the information we need. Now we know what they look like, there is no way they will ever be able to sneak into your body without us knowing. You need never worry about the same type of measles again.