The course of development of L. enrietti infection in normal and immunosuppressed guinea pigs was studied. The leishmanial lesion in normal guinea pigs is confined and self-limiting, but in immunosuppressed animals it metastasizes and diffuses to various parts of the body, particularly the extremities. Successful immunosuppression for such studies can be achieved by administering antilymphocytic antiserum, cyclophosphamide, or whole-body irradiation. All such immunosuppressants must be continuously applied to lower the total white blood cell count to about 2.000/ml and maintain it at that level.
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