How does the immune system work?
The immune system is a hugely complex system that stops us from getting sick or dying, it is like an army, fighting viruses and bacteria everyday. From tiny antibodies to large macrophages, every cell in the immune system plays a vital role in keeping us safe.
The first barrier of the immune system is the skin. Bacteria and viruses can’t get in unless the skin is penetrated. When something cuts your skin, nearby bacteria use the chance and enter through the wound. Once inside, they start to use up the body's resources and double in numbers every 20 minutes, they will go unnoticed until a certain number is reached and then they start to harm the body.
The first cells to arrive on the battlefield are macrophages. Macrophages are found all over the body and they can devour over 100 intruders each. They kill bacteria by swallowing it whole and then enzymes inside it break the bacteria down like our stomach acid to food. Macrophages also produce messenger proteins that tell the bloodstream to release water into the battlefield to make fighting easier for them, you may notice this as a mild swelling.
If the macrophages fight for too long, they will call in backup. They use messenger protein that can communicate location and urgency. These proteins then trigger neutrophiles, who leave their patrol routes in the blood and come to the battlefield. These neutrophils are extremely deadly fighters fighting so hard that they sometimes kill healthy body cells in the process, because of that, they have evolved to commit sucide after 5 days to prevent them from causing too much damage to the body.
If this is not enough, then the brain of the immune system kicks in, the dendritic cell. This cell is the most important cell in the immune system. First, it collects samples of the invaders and keeps them on its outer layer. The dendritic cell then has to make a critical decision, does it need antivirus cells or bacteria killing cells. Right now, it needs bacteria killers. The dendritic cell then travels to the closest lymph node to activate T-cells.
T-cells are one of the most important cells in the immune system. When T-cells are born, they go through a complicated training process, of which only a quarter survives, those remaining cells are equipped with a specific setup on their outer layer. They then go to a lymph node, and wait for a dendritic cell to ‘activate’ them.
When the dendritic cell reaches the lymph node, it starts looking for a T-cell with just the right setup to vanquish this certain type of enemy. It does this by ‘bumping’ into heaps of different T-cells until it finds one with a setup that can bind to the intruders it has displayed on its outer layer and when it does find one, a huge chain reaction happens.
The T-cell is activated. It then duplicates hundreds of times. Some of the T-cells turn into ‘killer’ T-cells and head to the field of battle to help macrophages and neutrophils, while some others turn into memory T-cells that will remember that specific enemy and make you practically immune to that enemy in the future. But most of them travel even further into the lymph node to activate a very powerful cell, the B-cell.
Like T-cells, B-cells are born with a specific setup. When a T-cell and a B-cell with the same setup meet, the B-cell rapidly duplicates hundreds of times and then starts to produce millions upon millions of tiny little weapons, called antibodies.
Antibodies are tiny Y-shaped proteins that are specifically made to latch to a certain type of bacteria. The T-cell tells the B-cell what type of ‘bind’ they need for this particular invasion.
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The antibodies are now heading straight to the battlefield. When they arrive, they flood the battlefield killing or stunning hundreds of bacteria, the battle has now turned sides. The antibodies kill or stun the bacteria by ‘latching’ onto them with their specifically designed ‘arms’.
If they have only stunned the bacteria, macrophages are extremely good at eating the helpless bacteria.
With the new backup, the immune system can now vanquish the bacteria. At this point, hundreds of body cells have already died and without the constant battle signals, the remaining cells commit suicude, as to not waste the body's resources. But some cells stay behind, the memory T and B-cells, these cells will remember this certain enemy and will react so quickly if it is ever encountered ever, they will deal with it before you even know it is there. That is why you will only ever get one bad dose of the chicken pox.
This whole process can take anywhere from 3 days to 3 weeks depending on the type of bacteria/virus. From the bacteria entering your body, to macrophages and neutrophils, from the dendritic cell to T and B cells and finally antibodies. The immune system is complex but lifesaving. If we didn’t have our immune system, we would be, well, dead!
