Influence of Immunologic Competence of the Host on Metastases Induced by the 3LL Lewis Tumor in Mice2

Abstract

The importance of host immunologic competence in the spontaneous metastasis of the 3LL Lewis carcinoma was investigated. Immunologic impairment was induced in C57BL/6 and C3HeB mice by sublethal irradiation, adult thymectomy plus irradiation, or neonatal thymectomy, and the mice were later challenged with 5 × 10⁵ 3LL tumor cells subcutaneously. The number of lung metastases was significantly increased in these immunologically impaired animals, as compared with intact controls. Furthermore, immunologic restoration of these mice by injection of lymphoid cells or by thymus reimplantation reduced significantly the number of metastases when compared with the number in nonrestored mice. Immunologic impairment had a more striking effect on metastasis than on primary tumor growth; this suggested that the immunologic response of the host was more efficient with disseminated tumor foci than with a single tumor mass.