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. Author manuscript; available in PMC: 2013 Jan 1.
Published in final edited form as: Curr Opin HIV AIDS. 2012 Jan;7(1):50–57. doi: 10.1097/COH.0b013e32834ddcf2

Figure 2.

Figure 2

Epigenetic modifications at the PD-1 locus are coupled to persistence of antigen. During an acute viral infection (green line) the PD-1 locus in early effector antigen-specific CD8 T cells becomes unmethylated (open lollipops) and the chromatin more accessible relative to naïve and memory CD8 T cells. Functional memory CD8 T cells have reacquire a unique DNA methylation pattern (filled lollipops) relative to their naïve precursors. Exhausted CD8 T cells retain an unmethylated and accessible PD-1 locus during chronic viral infection (red line). Anti-retroviral therapies can reduce viral load, but it remains to be determined if the PD-1 locus becomes remethylated in exhausted virus-specific CD8 T cells.