Adult C3H mice responded to the grafting of a syngeneic sarcoma with a vigorous hyperplasia in the regional lymph nodes and spleen. These changes, otherwise progressive until the death of the animals, were reversed when the tumor was removed surgically. The hyperplastic response was not seen in animals previously immunized to the same tumor nor was it seen in tumor-bearing animals displaying concomitant immunity in response to a challenge of the same tumor. In fact, an inverse relationship was observed between the capacity of the tumor to induce transplantation resistance versus the growth rate of the tumor and the magnitude of the lymphadenopathy. These reactions were all found to be tumor specific. Histologically, the hyperplasia was seen to be due to a plasmacytosis and histiocytosis of the involved lymphatic tissue. An evaluation of the immune capacity of these animals to nonrelated antigens was undertaken. The response of tumor-bearing animals to sheep red blood cells, as measured by the Jerne plaque assay, and their capacity to mount a graft-versus-host reaction, as measured by the Simonsen assay, were both comparable to normal controls. Thus significant immunosuppression by the tumor was not seen.

It is suggested that a specific defect exists in the regional nodes, possibly due to the “weak” nature of the tumor antigens, and that the tumor becomes established irreversibly before an effective immune response develops. The massive plasmacytosis and histiocytosis are probably in response to an established, progressively growing tumor releasing large amounts of antigenic material and suggest that antibody, possibly “blocking” antibody, is being produced.

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Conducted under American Cancer Society Grant IC-41C, USPHS Contract NIH 69-2061, and USPHS Grant CA 08832. Supported in part by Cancer Training Grant CA 8101. Also supported by USPHS Grant CA 39382.

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