Further, the robust START study published in 2015 highlighted net differences in serious events and all-cause mortality between those who started treatment with a high CD4 (>500 cells/μL) compared with those who delayed treatment start until CD4 had dropped to 350 cells/μL.13 The immediate start of treatment was found to significantly reduce the rate of both AIDS and non-AIDS events. This evidence concerns the gene CD4 and AIDS.