Azathioprine (Imuran) administration and the development of malignant lymphomas in NZB mice

Abstract

Azathioprine in doses that made NZB mice more anaemic did not cause reversal of their positive Coombs tests. When given to young NZB mice it did not delay development of the Coombs positive state.

Azathioprine had a carcinogenic effect. Six out of eight NZB mice treated from the age of 2 months developed malignant lymphomas particularly involving the thymus.

Caution is suggested in the use of immunosuppressant agents in non-malignant conditions, especially in the young, until the risk of carcinogenesis has been evaluated.