Biologic properties of iscador: a Viscum album preparation I. Hyperplasia of the thymic cortex and accelerated regeneration of hematopoietic cells following X-irradiation.

We demonstrated that a preparation of Viscum album (Iscador) has unusual effects on the immune system. In CD-1 mice, the mean weight of the thymus increased from 45 to 85 mg. following six daily intraperitoneal injections of 2.5 mg. of Iscador. The thymic trophic influence was maintained over a long period of time. Sprague-Dawley rats treated with Iscador for 16 weeks showed an increase of 78% in thymic weight over controls. The increased weight of the thymus was due to increased proliferation of cortical thymocytes. The number of blast cells in the outer cortex of the thymus increased within 2 days of the first injection and remained at high levels. Thymocytes of Iscador-treated animals were 29 times more responsive to Concanavalin A than those of untreated controls. Iscador increased the amount of antibody produced by animals injected with sheep red blood cells if it was injected after the antigen. Iscador also had effects on hematopoietic cells. It accelerated the recovery of hematopoietic tissue in bone marrow and spleens of irradiated animals. We believe that V. album preparations may be valuable reagents for perturbing thymus function.