Antigens
An antigen is any molecule that your immune system can recognise.
Bacteria, viruses, and other things that can cause infections all have different antigens.
Your own cells carry lots of different antigens on their surface. Different types of cells have different antigens. These antigens can change if a cell is infected or damaged.
Your immune system looks at these antigens to see if something should be in your body or not. A bit like checking an ID card.
These checks are done by immune cells and antibodies.
Antibodies
Antibodies are a type of protein. They are made by immune cells called B cells. It is thought that the human immune system can make about 10 billion different antibodies. All of these will stick to something different.
When an antibody sticks to an antigen it is like raising a red flag, calling on your immune system to attack.
T cells and B cells
Immune cells called T cells will kill the cell that the antibodies have stuck to. Other parts of your immune system will clear up the mess.
You will also make cells called memory B cells. These remember the antigen and can stay on the lookout for it in your body for many years. So if you get the same infection again, your immune system will be ready and able to respond quicker. This is why you can become immune to some infections after having them the first time.
What goes wrong in autoimmune conditions?
In autoimmune conditions, your immune system starts to make antibodies that stick to your own healthy cells. These are called autoantibodies.
Each different antibody will only stick to one very specific marker. So these rogue autoantibodies will stick to one type of cell in your body. For example cells found in your liver or in your bile ducts.
When this happens your immune system will treat those cells as dangerous and attack them. This damage then leads to liver disease.
Key words
Antigen a marker on the surface of a cell or virus that can be used to identify it.
Antibody a protein that can stick to a specific antigen and trigger an immune response.
Autoantibody an antibody that sticks to normal healthy cells causing an autoimmune response.
B cell a type of white blood cell that makes antibodies, also called a B lymphocyte.
Memory B cell a type of B cell that remembers and looks out for an antigen that has been dealt with before.
T cell a type of white blood cell with lots of jobs, including killing cells that antibodies have stuck to. Also called a T lymphocyte.
What causes autoimmune conditions?
It is not always clear why someone develops an autoimmune condition.
Sometimes autoimmune conditions can run in families. This means that there are slight differences in the genes passed from parents to children. But these different genes do not usually cause autoimmune liver disease on their own.
The inherited change can increase someone’s risk. But an external trigger is usually needed to cause a problem.
The trigger is something from outside the body. Such as a virus, a severe side effect from a medicine, or something in the environment like cigarette smoke. We usually do not know what the trigger was for each person.
Developing one autoimmune condition could mean you are more at risk of getting others.
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Find out morePublished: July 2024