Effects of radiation and other influences on chemical lymphomagenesis

Methylnitrosourea (MNU) or butylnitrosourea (BNU) was used to induce T cell lymphomas (thymomas) in BDF1 mice. In addition to the chemical, X-rays in various dose schedules were applied. An effect of the irradiation (shortening of the latency period) was seen with 12 X 0.25 Gy in protocols with a prolonged median induction time in the controls as a result of a dose reduction of the chemical (median induction time 27-36 weeks instead of 16-18 weeks under 'optimal' conditions using 50 mg kg-1 of MNU). Preirradiation 2-5 weeks before 40 mg kg-1 of MNU resulted in enhanced leukaemogenesis. Also, mice with regenerating lympho-haemopoiesis after lethal irradiation and bone marrow transplantation were more sensitive to the effect of both chemicals than were the controls. Treatment with anti-thy 1.2 and with corynebacterium parvum during the latency period had no influence.