Cell adhesion inhibitors (natalizumab) compromise the cellular (CD4 and CD8 lymphocytes) surveillance in the CNS and may predispose not only to progressive multifocal leukoencephalopathy, a John Cunningham (JC) virus, but also to herpetic and varicella zoster encephalitis.18 Here, CD4 is linked to progressive multifocal leukoencephalopathy.