Spontaneous LCLs and neoplastic cells of the same HD patient are derived from independent EBV infections. Southern blot analysis performed on BamHI-digested DNAs hybridized with a probe corresponding to a region flanking the 5′ terminal repeats of EBV genome. (A) and (B) DNA from two pathologic lymph nodes from case HD-3; 1 and 2, DNA from two spontaneous LCLs derived from one lesion of the same HD patient; 3 to 6, DNA from four LCLs obtained by spontaneous outgrowth from the PBMCs of the same patient; N, DNA from a colon carcinoma cell line; (C) DNA from an EBV⁺ Burkitt's lymphoma as a positive control. Sizes are in kilobases.