Cyclin A expression in Tg B-cell malignancy. RT-PCR was performed with RNA from purified B cells (Tg B cells) or purified T cells (Tg T cells) from spleens of asymptomatic Tg mice, using primers to the cyclin A gene. Results were compared with negative control (–RT) and to RNA from B cells obtained from independently arising B-cell lymphomas in 6 different mice. Lymphoma lane 1, Tg leukemic mouse (transplant donor); lane 2, Tg^mut leukemic mouse; lane 3, second serial transplantation; lane 4, second serial transplantation; lane 5, fourth serial transplantation; lane 6, fourth serial transplantation.