Epstein-Barr (EBV) is a powerful immortalizing virus for human B lymphocytes in vitro and is associated with several human neoplasias in vivo. Previously, we have shown that the majority of EBV-infected cells in the peripheral blood of healthy, persistently infected individuals do not express the activated phenotype, e. g. , high levels of cell surface CD23 and CD80 (B7), characteristically expressed on in vitro-immortalized cells. Here, we show that > or = 90% of the CD23-, virus-infected cells in the peripheral blood are in G0 and therefore resting VSports手机版. The remaining cells may be G1 arrested, but we were unable to detect a significant number of cells traversing the S-G2-M stages of the cell cycle. The mRNA for LMP2A, but not EBNA1 originating from Qp, was readily detected in this population, and these cells appear competent in the processing and presentation of antigen by class I major histocompatibility complex. We propose that these resting B cells are the site of long-term latent persistence for EBV. We further propose that the persistence of the virus in a resting B7- B cell provides an important mechanism to escape immunosurveillance. The demonstration that EBV can persist latently in a resting B cell means that the immortalizing functions of EBV can be down regulated in a normal B cell. This conclusion has important implications for understanding and controlling EBV-associated neoplasia. .