How the immune system and inflammation work

How the immune system and inflammation work

A person with rheumatoid arthritis (RA) has an immune system that works differently from that of others. Understanding the effects of RA begins with understanding how the immune system and inflammation work. So here is a simple explanation!

How does the immune system work?

First of all, inflammation is what happens when the immune system is activated. The body's immune system uses inflammation as a protection. It is a completely natural process that in most cases is good because otherwise, we would have no effective defense. However, in people with chronic inflammatory diseases, the inflammatory process does not return to a "non-attacking" state. That creates problems for the body because it ends up in a chronic inflammatory condition, as is the case in RA. To better understand what happens in RA, we need to understand more about how the immune system works.

External and internal defence

Our immune system protects us from bacteria, viruses and other foreign organisms. The body has both external and internal defenses that co-operate. The external defense consists of, among other things, skin and mucous membranes, which makes it difficult for bacteria and viruses to penetrate and infect the body. If something does penetrate, the internal defenses take over. There are many different components here, including the white blood cells that attack foreign substances. When internal defense is activated, white blood cells flow to the area, where they have many tasks. Among other things, they eat up damaged tissue and act as "beacons" or "companions" to draw attention to the fact help is needed by other aspects of the internal defense system.

What starts an immune response?

Inflammation occurs when the body's tissue is damaged in some way. It could be, for example, a wound, an overload, or infection by a virus, fungus or bacteria. Signs of active inflammation include redness, swelling, pain, and that the area on the body feels hot. In severe inflammation, you can also get a fever, caused by the body producing fever-activating proteins. When you have an autoimmune disease such as RA, the immune system does not work in the same way as a healthy person's immune system, but also attacks the body's own cells.


One kind of white blood cell, called B cells, produce antibodies. Antibodies are a type of protein that mark cells perceived as a threat. In an attack from foreign substances, this is a very effective way to protect the body. This process is important so the immune system knows which cells are approved and which are unwelcome. The immune system then attacks cells marked as a threat. For those who have an autoimmune disease, however, something has gone wrong. Some of the body's own cells have been perceived as a threat and have been marked, so the immune system attacks them.


In the Elsa app, you can log your pain and fatigue, which means you can follow your mood over time, see patterns and understand what affects you.


  1. Mihai G Netea, A guiding map for inflammation. Nature immunology, 18 (8), ss.826-831.

  2. Abul K. Abbas, (2014) Cellular and Molecular Immunology. Distinguished Professor and Chair, Department of Pathology, University of California San Francisco, San Francisco, California.