Skip to main content

Alert COVID-19

Please find service updates and current visiting rules in our COVID-19 section.

This site is best viewed with a modern browser. You appear to be using an old version of Internet Explorer.



Autoimmunity is the process behind inflammatory diseases. The immune system is present to protect us, but in autoimmunity it becomes confused and auto reacts - this means it attacks the body, such as the joints, without specific cause.

The immune system is a complex network of cells, proteins and chemical reactions that protect us from infection by viruses and bacteria. It also helps with other processes, such as healing. Components of the immune system include white cells (called lymphocytes and neutrophils), and proteins (such as immunoglobulins, also known as antibodies, and complement).

In autoimmunity, these cells and proteins attack a part of the body as though it were an infection. Because there is no infection it cannot be cleared and the immune reaction continues to act indefinitely or until the balances and checks of the immune system come into place.

These balances and checks are in constant adjustment. In autoimmunity they are sometimes effective at controlling inflammation at other times they are not. This is why inflammation occurs in waves or flares.

It is important to remember these natural flares and troughs in disease activity when judging the effectiveness of a treatment. It is also important to mention flares when telling others (such as school teachers) about the condition. This is because the appearance and disappearance of inflammation can be confusing to those who are not familiar with autoimmunity or inflammatory diseases.

Autoimmunity happens in us all. At low levels it helps to make the immune system more effective and stronger. In people with inflammatory diseases this autoimmunity is not controlled and causes harm.

Why some people should have excess autoimmunity is not entirely clear. It is likely they have risk factors in their genetic make up. But it is only when there are environmental triggers, such as a minor infection, that this risk factor will be converted into a autoimmune / inflammatory disease.

Autoimmunity treatment

Because the immune system is so complex, it has not been possible yet to identify a cure. However, we have medicines that target certain cells or proteins to reduce inflammation, pain and loss of function. These anti-inflammatory (or immunomodulatory) drugs reduce the number of flares and the severity of each flare.

In some patients, anti-inflammatory drugs put the inflammation into remission for long periods of time - sometimes indefinitely. In most cases they prevent damage to the tissues in the long term.


Inflammation is normally helpful. At times of infection, trauma or other causes of harm to the body, inflammation plays a very important role in protecting the injured tissue from further infection and starting the healing process. It does this by increasing blood flow to the damaged tissue to both deliver important blood cells and proteins and wash away unwanted breakdown products or debris.

This process of inflammation is best seen in the skin. Inflammation appears red and hot because of increased blood flow and the intense activity of cells. These cells leak into the skin tissues along with fluid and proteins from the blood to produce swelling. Sometimes, as with inflammation of infection, high collections of cells appear as pus. The same process occurs in all parts of the body whenever injured.

In an inflammatory disease, inflammation occurs by mistake. Increased blood flow and cells arrive at a given site, causing heat, swelling, pain and loss of function, but there is no infection and no trauma has occured. Attacking the body without an external insult in this way is called autoimmunity.

This is what happens in arthritis. The tissue that swells is the lining of the joint and increased fluid is produced. Together these make the joint swollen, painful and stiff to move. There is also loss of function - for example, a swollen knee makes it difficult to walk.

Inflammation can also cause:

  • enlargement and loss of function of the kidney (as in SLE)
  • swelling and loss of function of blood vessels (as in Vasculitis)
  • swelling and loss of function of muscles (as in Juvenile Dermatomyositis).

In fact, any organ can be affected in this way.

The overall effect of this inflammation depends on how long it lasts. Short periods of inflammation, such as with an allergic reaction or reactive arthritis, are generally fully resolved and leave no long-term problems.

Inflammation that lasts several months or years, or is particularly severe, may cause lasting damage to the affected area or organ (for example, leading to deformed joints). This is what happens in arthritis.

Inflammation treatment

Severe inflammation can be treated very quickly with intravenous steroids. These are usually given over a period of 2-4 hours so patients can be treated as day cases.

A one-off dose may be used, but generally we give one or two courses (one dose each day for three days).

Oral steroids are often continued afterwards.

Juvenile Idiopathic Arthritis (JIA)

Arthritis in children is called Juvenile Idiopathic Arthritis, or JIA for short.

  • Juvenile means it happens before the patient is 16 years old
  • Idiopathic means we don't know what causes it
  • Arthritis means joint swelling

For more information please visit:

Versus Arthritis - Juvenile Idiopathic Arthritis (JIA)

Last reviewed:10 October 2022