Figure 4: NK cell phenotypes expressing the surface marker CD57. In the CFS/ME group, a significant increase was observed in CD56dimCD16+ NK cell expression of CD57. CD56dimCD16+ NK cells expressed significantly increased amounts of CD57 in comparison to CD56brightCD16-/dim and CD56dimCD16- NK cells from both groups. Data is presented as mean ± standard error of the mean (*P<0.05 and **** P<0.0001).