Objective: Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME) is a debilitating illness with no known cause. Functional and phenotypic immunological alterations may be playing a role in the illness pathomechanism as immune dysfunction is common in CFS/ME. Studies have also inferred that this immune dysfunction may be further jeopardised in severe CFS/ME patients. The purpose of this study was to provide an analysis of natural killer (NK) and CD4+ T cell receptors in CFS/ME patients who were moderately affected by symptoms compared to those who were severe. Methods: The 1994 Fukuda criteria for CFS/ME were used to confirm CFS/ME participants. Participants were age and sex matched into the groups of healthy controls (n=18), moderate (n=15) and severe (n=12) CFS/ME patients. Flow cytometry was used to examine NK cell adhesion molecules and CD4+ T cell receptors on the four main phenotypes of each cell. Results: Moderate CFS/ME patients had reduced LAG3 and KLRG1 in CD4+ T cells and reduced CD2 expression in NK cells compared to severe CFS/ME patients. Severe CFS/ME patients also expressed increased CD18+/CD11c- and reduced CD18+/CD11a- in CD56dimCD16- NK cells.
Conclusion: NK cytotoxic activity is the result of NK and T cell receptor interactions, with alterations in CFS/ME potentially leading to a dysregulation of target cell lysis and receptor regulation in patients. This study also highlights the importance of assessing symptom severity in CFS/ME patients in both clinical and research settings. Key Words: Chronic Fatigue Syndrome, severity, Natural Killer Cell, receptors, CD4+ T cell, adhesion