-ID expression evaluated by RT-PCR. (A) LTMC adherent layers from all dogs and (B) blood (PB) and marrow (BM) leukocytes from M2 at 1 to 3 months postinfusion. PCR amplification of a 618-bp proviral specific -ID transcript (proviral transcript) was performed. PCR amplification of the 422-bp transcript arising from either the normal or mutant genomic -ID cDNA (endogenous transcript) was performed to confirm the presence of amplifiable cDNA in these tissues. A control for each sample was not treated with reverse transcriptase (RT−) to ensure that there was not genomic DNA contamination of samples. Abbreviations: ULTMC, untransduced LTMC control from M2; RC, reagent control; +C, positive control DNA.