Immune Response to a Transplantable Malignant Melanoma in Mice2

Abstract

Humoral immune response to the B16 melanoma in its syngeneic host, the C57BL/6J mouse, in volved production of complement-fixing, cytotoxic, and reaginic antibodies to B16 antigens. Lymphocytes that were stimulated to DNA synthesis when cultured with B16 antigens were present in the spleen and regional lymph nodes. Lymphocytes capable of inhibiting B16 growth in vitro were in the spleen but not in the regional lymph nodes during tumor growth; in contrast, lymphocytes of the regional nodes stimulated B16 growth in vitro. Serum collected during tumor growth converted from inhibitory to stimulatory the action of immune spleen lymphocytes on 816 growth. Macrophages in the tumor increased in number during tumor growth; histopathologic examination of the growing tumor revealed an early, transient, lymphocyte infiltrate and later macrophage involvement. The blood, spleen, and regional-node lymphocyte response to phytohemagglutinin decreased as the tumor grew. We concluded that absence of cytotoxic lymphocytes in the regional nodes, serum-mediated conversion of the effect of immune lymphocytes from inhibitory to stimulatory action on B16 growth, and anergy ofthymus-derived lymphocytes allowed the B16 tumor success over its host.