Prevention by splenectomy of thymus weight depletion in the presence of progressively growing tumor in rats: Brief communication.

Groups of inbred rats were inoculated with the Walker 256 carcinosarcoma. The weights of their spleens and thymuses were determined on days 16 and 23 after the tumor inoculation. Spleen weights increased progressively as the tumors grew (P less than 0.001 on day 16 as compared to controls, much less on day 23). Thymus weights decreased at the same intervals (P less than 0.05 on day 16 as compared to controls; P less than 0.001 on day 23). In other groups of inbred rats, splenectomy was performed 5 days prior to tumor inoculation. If splenectomized animals were not inoculated with tumor, thymus weight did not change. Previously splenectomized, tumor-bearing animals also showed no decrease in thymus weight on day 16 or 23. Thymus weight remained greater in splenectomized, tumor-bearing animals than in intact, tumor-bearing animals on day 16 (P less than 0.05) and on day 23 (P less than 0.001). Microscopic examination of thymuses on day 23 revealed some depletion of cortical lymphocytes in splenectomized, tumor-bearing animals and profound depletion of these lymphocytes in intact, tumor-bearing animals. Tumor weights and measurements did not differ between splenectomized, tumor-bearing and intact, tumor-bearing animals. Equal rates of tumor growth provided for a roughly equal tumor burden at termination of the experiment.