First, CCR5 is widely expressed on the cell surface of activated CD4+ or CD8+ T cells.26 The wide CCR5 expression on brain lesion-infiltrating CD8+ T cells demonstrated in inflammatory PML could therefore only reflect the activation of effector T cells, without indicating an implication of the CCR5–CCL3/CCL5 axis in migration and homing of CD8+ T cells to the CNS in PML-IRIS. This evidence concerns the gene CD4 and progressive multifocal leukoencephalopathy.