CD4 and HIV-1 infection: 23 Kaufmann Kaufmann GR GR Perrin Perrin L L Pantaleo Pantaleo G G CD4 T lymphocyte recovery in individuals with advanced HIV-1 infection receiving potent antiretroviral therapy for 4 years: the Swiss HIV cohort Study CD4 T lymphocyte recovery in individuals with advanced HIV-1 infection receiving potent antiretroviral therapy for 4 years: the Swiss HIV cohort Study Arch Intern Med.