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Tumor-specific Immunity in the Course of Primary Polyoma and Rous Tumor Development in Intact and Immunosuppressed Rats¹

Department of Immunology, Fred Hutchinson Cancer Center, Pacific Northwest Research Foundation, Seattle, Washington 98104 [H. O. S.], and Department of Pathology, University of Lund, Lund, Sweden [K. B.]

The development of cell-mediated immunity and the appearance of a blocking serum activity capable of nullifying the lymphocyte effect has been followed during polyoma and Rous virus tumorigenesis by use of the in vitro colony inhibition test. Lymphocytes specifically immune to the tumor antigen in question were demonstrable whether or not the animals had been subjected to immunosuppressive treatment (antilymphocytic serum during the latency period or neonatal thymectomy before virus infection). Such immune lymphocytes were present to about the same extent in lymph nodes of rats that carried primary tumors and of virus-infected rats that had not yet developed any tumors, and in rats carrying primary Rous sarcomas they were detected in the thoracic duct lymph as well. A blocking serum activity was found in 22 of 23 rats bearing primary polyoma tumors and in 8 of 10 rats carrying primary Rous sarcomas. Sera of all 13 previously immunosuppressed rats carrying primary polyoma tumors had a blocking activity. No such activity was detectable in three rats which did not develop primary polyoma tumors. Sera obtained 1 to 13 weeks prior to the appearance of visible primary tumors were sometimes blocking (in three of seven polyoma rats and one of four Rous sarcoma animals). The blocking serum activity is tentatively attributed to blocking antibodies, which mediate an efferent form of immunological enhancement.

¹ This work was supported by grants from The Swedish Cancer Society (Projects 116-K69-03Xa and 274-B69-01X) and NIH Grant CA-11742.

Received 11/ 3/70. Accepted 2/23/71.