CD38 and lymphopenia: For memory CD4+ T-cells, we found that, although proliferation rates were associated with viral load (Supplementary Figure 2A) and CD4 lymphopenia (Supplementary Figure 2B), the strongest association was with immune activation (HLA-DR/CD38 coexpression; Supplementary Figure 2C), although it should be noted that no markedly lymphopenic subjects were recruited.