Flow cytometry protocols assessed CD56dim CD16+ and CD56bright CD16+/- NK cell expression of adhesion molecules, NK activating and inhibiting receptors, NK cell maturation and lytic proteins. All participants in this study were female and included 14 CFS/ME patients, 9 MS patients and 19 non-fatigued controls. The patient groups and the non-fatigued controls were not taking any immunosuppressive or immune enhancing medications. In the MS cohort, KIR2DL5 was significantly increased on CD56bright CD16+/- NK cells and expression of CD94 was significantly increased on CD56dim CD16+ NK cells in comparison to the controls. Co-expression of CD57 and perforin was significantly increased on CD56dim CD16+ NK cells from CFS/ME patients compared to the MS and non-fatigued control participants.
The results from this pilot study suggest that NK cells from CFS/ME and MS patients may have undergone increased differentiation in response to external stimuli which may affect different mechanisms in the NK cell cytotoxic activity pathway.