TRAF1 expression negatively correlates with PD-1 levels and viral load. PBMCs from HIV-infected individuals were stained for CD3, CD8, HIV-tetramer, PD-1, and TRAF1. (a, top) Percentage of PD-1⁺ HIV-specific CD8 T cells is plotted against percentage of TRAF1⁺ HIV-specific CD8 T cells from the same chronically HIV-infected donors, with each symbol representing a single epitope from an individual donor. (bottom) Representative FACS plots of PD-1 and TRAF1 expression gated on HIV-tetramer⁺ CD8 T cells from three representative donors. Note: if we remove the extreme value point for the one donor with low PD-1 and high TRAF1, the correlation becomes r = −0.48, with a P value of 0.038. (b) Percentage of TRAF1 expression in HIV-specific CD8 T cells from the chronic stage of HIV infection, including both chronically infected donors and viral controllers, is plotted against log viral load recorded for each donor in Table S1. Each data point represents a single donor.