CD4 and HIV-1 infection: The use of mass cytometry may offer a unique possibility to assess the relationship of markers present on T cells with the size of HIV-1 reservoirs; this approach does not target HIV-1 specific CD4 + and CD8 + T cells but may rather contribute to pin-point dysfunctional features of the whole T cell population during HIV-1 infection, which may indirectly affect the size of the reservoir.