Epstein–Barr virus (EBV) loads in peripheral blood mononuclear cells (PBMCs) from 29 normal individuals and 24 patients with systemic lupus erythematosus (SLE). (a) Sensitivity of PCR/Southern blot for the EBV nuclear antigen (EBNA)-3C sequence. DNA was purified from serial 10-fold dilutions of Namalwa cells (corresponding to 1 to 1 × 107 cells) were mixed with BJAB cells to yield a total cell number of 1 × 107. PCR was performed using a 100th of the purified DNA (corresponding to DNA of 105 cells). The PCR products were separated in an agarose gel, transferred to a membrane, and probed with an EBNA-3C-specific oligonucleotide. (b) EBV loads of normal individuals and SLE patients. The mean EBV load of each group is presented as a heavy horizontal line.