One of the most consistent abnormalities reported in ME/CFS patients over the past 20 years has been that their natural killer cells are reduced in number and/or have a lower activity than in healthy people. In fact, there was a suggestion at one time that an alternative name for the illness might be ‘low natural killer cell’ disease. Natural killer cells have a key role in the targeted killing of tumour cells and virus infected cells, so it is important that they are present in optimum numbers and that they are as active as they can be. No-one knows, however, whether natural killer cell activity is consistently lower in the illness, or whether it simply changes over time as, for example, patients relapse and recover.

Researchers at Bond University, Australia, decided to look at the activity of natural killer cells and other cytokines over 12 months in 65 ME/CFS patients and 21 non-fatigued healthy controls. The cytotoxic activity of natural killer cells (i.e., their ability to destroy other unwanted cells) was found to vary significantly in patients over the 12 months, but was nevertheless consistently lower throughout the whole year in the patients than in the non-fatigued control group. The authors point out that this decrease in immune function is similar to what is seen in various immunological diseases, and suggests an increased susceptibility to viral and other infections.

Reference: Longitudinal investigation of natural killer cells and cytokines in chronic fatigue syndrome/myalgic encephalomyelitis. Brenu EW et al. J Transl Med 2012 May 9; 10: 88.