Lymphoreticular tissue lesions in mice after immunization with typhoid fever vaccine and immunosuppression with azathioprine.

C57BL and Balb/c mice were immunized, were immunized and then administered immunosuppressives, were immunized with concurrent immunosuppression, and were immunized after prior administration of immunosuppressive agents. Typhoid fever vaccine used clinically was used for immunization. Immunosuppression was accomplished with azathioprine (Imuran). Control groups received azathioprine or no treatment. The experiment lasted 5 months. In mice immunized with typhoid fever vaccine and subsequent azathioprine administration, malignant lymphomas of a lymphoblastic type appeared in 20% of C57BL mice and in 70% of Balb/c mice. In mice receiving antigenic vaccine together with azathioprine, malignant lymphomas appeared in only 5 to 10% of cases. However, mice that first received azatioprine and were later immunized, died after the second administration of typhoid fever vaccine and showed pictures that brought to mind blastic transformation of lymphocytes in vitro. This proliferation was primarily found in subcortical areas of lymph nodes. Analysis of presented results indicates that chronic immunization of animals with typhoid fever vaccine may serve as experimental model of malignant lymphoma morphologically similar to that appearing in human pathology.