Antilymphocyte antiserum effect on incidence of spontaneous malignancy. I. Long term treated mice

Long term potent immunosuppression was administered to normal 7-week-old BALB/c mice without exogenous neoplastic induction. Antilymphocyte antiserum was given biweekly for 8 weeks and azathioprine daily for 347 days. Significant immunodepression was demonstrated after 348 days of theraphy. After 2 years, all animals were sacrificed and examined for neoplasia. There was no evidence that such immunodepression increased the incidence of spontaneous malignancy. The study suggests that immunosuppressive therapy is not inately oncogenic.