Medical Matters > Low-level Immune System Activation

ME Essential Winter 2024


I keep seeing references to ‘low level immune system activation’ being an important research finding in ME/CFS.  But what does this mean in language that I can understand?


In very simple terms, the immune system is a bit like an army in that it has many different components – all with different jobs to do when it has to deal with an invader in the form of an allergy or an infection. 

We know from numerous research studies into ME/CFS that if you look very carefully at the immune system you can find abnormalities in many of these different components – antibodies, autoantibodies, T cells and cytokines to name but a few. But none of them are sufficiently consistent or significant to link in with symptoms – with the possible exception of cytokine dysfunction. 

Cytokines are one of the front line troops of immune system chemicals that are produced during the very early stage of an infection. They also help to produce the characteristic symptoms of any infective illness – fatigue, muscle and joint pains, loss of appetite, increased sleep requirements etc. 

One of the more consistent abnormalities in recent research into immune system dysfunction in ME/CFS involves increases in specific types of cytokine. And this makes some sense in relation to a link to symptoms because ME/CFS involves feeling as though you have a constant dose of flu. Because this type of cytokine abnormality equates to immune system activation we tend to refer to this finding in ME/CFS as being low-level immune system activation. 

Further support for immune system activation comes in the form of an interesting brain scan research study from Japan. This research found evidence of what is called neuroinflammation, which could be linked to increased levels of these inflammatory chemicals entering the brain and central nervous system. We use the term low-level because this is a fairly subtle abnormality concerning cytokine production and not the massive release of cytokines that accompanies an acute infection. 

Useful research reference on cytokine abnormalities in ME/CFS: 

  • If you want to follow this up in more detail, the cytokine and neuroimaging research is summarised and referenced in the Immunology and Neuroimaging sections in the chapter on Research in the MEA Clinical and Research Guide (‘The Purple Book').


Information provided by The ME Association should not be construed as medical advice. Don't assume any new or worsened symptoms are simply the result of having ME/CFS or Long Covid. We recommend that any information you deem relevant is discussed with your NHS GP as soon as possible. It is important that you seek personalised medical advice from the GP who is in charge of your care and who knows you well.

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