Southern blot analysis of p16 gene deletion in five patient specimens. (A) DNA samples digested with EcoRI and hybridized with p16 exon 2 probe revealing a band of 4.3 kb for normal DNA only (lane 1), which is not present in 1 patient specimen (lane 5). (B) The same blot was rehybridized with a probe for the IL-2RB gene, demonstrating the presence of DNA in all lanes.