CD4 and HIV-1 infection: HIV-1 infection of CD4+ cells primarily involves a prominent subset of T lymphocytes and myeloid cells, the latter of which encompass very different cell types, such as myeloid dendritic cells, circulating monocytes, eventually extravasating to become MDM in inflammatory conditions, and TRM that acquire very distinctive features according to the anatomical site (from Kupffer cells in the liver to the microglia in the CNS) [4,5].