Furthermore, as CD34+, CD38- stem cells can be differentiated in vitro to transiently express CD21 prior to commitment to T or NK cell lineage (CSL, unpublished observation), this raises the intriguing possibility that infection of a precursor cell has the potential to give rise to either or both NK cells and T cells carrying the same monoclonal EBV episomes. The gene discussed is CD34; the disease is infection.