PCR amplification of EBER transcripts. EBV-specific transcripts are amplified by single cell PCR of sorted IgG anti-CL B cells (A) and IgM anti-CL B cells (B) and analyzed on ethidium bromide-stained agarose gels. Products are visible as bands of 253 bp. Negative control of PCR (Cont -) and positive control (Cont +) are shown: cells infected with the B95-8 strain of EBV are used for the positive control.