For instance, some data support a possible predisposition for PML amongst those with type 0 red blood cells, and other data reveal that in HIV-infected PML patients the TCR shows multiple upstream Tat-responsive element (up-TAR) duplications, which is also constantly found at the 5′-end of HIV-1 mRNAs, and this region is involved in HIV Tat induction of the viral late promoter [35,36]. This evidence concerns the gene TAT and progressive multifocal leukoencephalopathy.