Influence of adult thymectomy on growth of transplanted tumors in mice

SUMMARY-Thymectomy of AKR and C3HeB mice at 4-8 weeks of age lowered their normal resistance to implanted tumors of foreign origin of the same or different H-2 transplantation locus. Five weeks after tumor implanta-tion, the level of peripheral blood lymphocytes of thymectomized animals that had rejected the tumor was significantly lower than that of their intact controls. When SBl-H, a tumor conditioned to the C3HeB strain, was used, the neoplastic implant grew in both thymectomized and intact recipients. However, tumor grafts growing in thymectomized animals lacked the usual lymphocytic infiltration found at the periphery of the tumors growing in the intact controls. Apparently the thymus still plays a significant and specific role in adult mice in relation to their homograft response to Foreign tumors.-J Nat Cancer Inst 41: 411-420, 1968. IT IS generally recognized that neonatal thy-mectomy severely damages the immunologic com-petence of the animals. Removal of the thymus o