Amplification of ltr -gag sequences in lung samples. Agarose gel electrophoresis of the 1338-bp PCR product using LTR5'-GAG3' primers (top panel). The 620-bp PCR product was amplified using the LTR5'-LTR3' primers (middle panel). As a PCR control, we used G3PDH primers to amplify a 452-bp product (bottom panel). Lane M contains a marker; lane 1 is INER51; lane 2 is IN6; lane 3 is HZ14; lane 4 is HZ101; lane 5 is HZ-19; and lane 6 is the negative control.