CD8A and myalgic encephalomeyelitis/chronic fatigue syndrome: We also analyzed several markers of immunosenescence or immune exhaustion, with discordant results: CFS and control individuals had similar expression of the T-cell immunosenescence marker CD57[46] in CD4 and CD8 T cells, while differences were observed in the expression of exhaustion markers PD-1 and CD95[46] in CD4 and CD8 T cells, respectively (Figure 3C).