CD4 and Opportunistic infection: Although any cut-off is somewhat arbitrary, we endorse a CD4+ threshold of 200 cells/μL for two reasons: (1) it is a threshold which provides protection against many opportunistic infections, some of which may be difficult to diagnose and may cause significant post-transplantation morbidity and mortality; and (2) with the exception of liver transplants, the safety of organ transplantation below this recipient CD4+ level has not been established, as trials have generally excluded patients with CD4+ counts below this level.