In this study, we aim to identify factors associated with the normalization of the CD4+:CD8+ T cell ratio among participants in the UK Collaborative HIV Cohort (UK CHIC) study, and to describe the association of CD4+ and CD8+ T cell counts, as well as the CD4+:CD8+ T cell ratio, with the risk of new AIDS events among individuals who achieve a suppressed viral load. Here, CD4 is linked to AIDS.