Mouse fibroblasts transformed by Rous sarcoma virus express a virus-specific non-virion transplantation antigen

Angiogenic effects of macrophages isolated from ascitic fluid aspirated from women with advanced ovarian cancer

The cellular components of ascitic fluid aspirated from the peritoneal cavity of women with advanced ovarian cancer were separated on a Ficoll gradient. Isolated macrophages, which were further purified, elaborated a growth factor which was mitogenic for human endothelial cells isolated from umbilical veins, arteries and the omental microvasculature in vitro, and was angiogenic in vivo. It is postulated that the macrophage-derived factor enhances tumor neovascularization of the widespread ovarian-derived peritoneal malignant lesions appearing in these patients, thus contributing to their rapid growth and metastasis, and the poor prognosis of the disease.

Macrophage infiltration and growth of sarcoma clones expressing different amounts of monocyte chemotactic protein/JE

Tumor-derived chemotactic factors (TDCF) have been identified and thought to play a role in the regulation of macrophage infiltration in neoplastic tissues. The present study was designed to assess the in vivo relevance of the TDCF molecularly identified as monocyte chemotactic protein/JE, by investigating murine sarcoma clones expressing different levels of MCP/JE. The 1D3 clone derived from the B77 RSV-induced sarcoma expressed appreciable levels of MCP/JE mRNA and, concomitantly, chemotactic activity for mononuclear phagocytes. In contrast, the 5B11 clone from the same tumor had undetectable levels of MCP/JE transcripts and little or no chemotactic activity. The chemotactic activity of 1D3 cells was blocked by an appropriate specific antiserum. The in vitro growth rate of the 2 sarcoma lines was identical. Upon in vivo transplantation, the 1D3 clone showed a substantially higher level of tumor-associated macrophages (28.9%; range 21%-34%) than the 5B11 clone (16.6%; range 13%-20%). 5B11-induced tumors appeared earlier and grew faster than those induced by 1D3. The difference in growth rate and in macrophage infiltration between 1D3 and 5B11 clones was also evident upon transplantation into nude mice. These results are consistent with the hypothesis that TDCF, identified as MCP/JE, is one important determinant of macrophage infiltration in tumors.

Monoclonal antibodies against murine gamma interferon

Monoclonal antibodies against murine immune interferon (IFN-gamma) were produced by fusing the murine nonsecreting myeloma cell line P3.X63.Ag8.653 with spleen cells from rats immunized with IFN-gamma-containing supernatants obtained by stimulating a T-cell lymphoma, L12-R4, with phorbol 12-myristate 13-acetate. Supernatants from a twice-cloned hybridoma (AN-18.17.24) were found to neutralize and to adsorb in depletion experiments up to 27 units of mouse IFN-gamma but not equivalent amounts of mouse leukocyte or fibroblast IFNs. The AN-18.17.24 monoclonal antibody neutralized to the same extent mouse IFN-gamma from different sources--namely, (i) concanavalin A-stimulated spleen cells, (ii) alloantigen-stimulated spleen cells, and (iii) monkey fibroblasts transfected with the cloned gene of murine IFN-gamma. Moreover, the monoclonal antibody displayed species specificity, since it did not neutralize IFN-gamma of human origin. Binding inhibition experiments with murine IFN-gamma preparations exposed to enzymatic or physicochemical degradation demonstrated that the protein moiety and not the carbohydrate residues were responsible for the binding to the AN-18.17.24 monoclonal antibody. Finally, this monoclonal antibody immunoprecipitated two molecular species of IFN-gamma of about 16.8 and 17.8 kilodaltons, respectively, from [35S]methionine- or [3H]glucosamine-labeled supernatants of stimulated L12-R4 cells.

Characterization of T lymphocytes mediating in vivo protection against RSV-induced murine sarcomas

Tumors induced by Rous sarcoma virus (RSV) in different mouse strains share a common tumor-associated transplantation antigen, whose expression is controlled both by the viral transforming src gene and by cellular gene(s) (Prat et al., 1981). The mechanism(s) responsible for the in vivo protective immune response against two RSV-induced sarcomas has now been investigated. In the "Winn assay" the growth of both tumors was specifically prevented or significantly reduced by the simultaneous administration of lymphocytes isolated from immunized donors. The effector cells were radiosensitive (2,500 rad), Lyt-1+, Lyt-2,3+ Thy.1+ cells. Better protection was afforded by transfer of immune spleen cells from mice pretreated with cyclophosphamide, which is known to abrogate T-cell suppressor activity. In a 5-day mixed lymphocyte/tumor cell culture specific anti-RSV-induced sarcoma cytotoxic activity was barely detected, while a good production of interferon-gamma (IFN-y) was observed. The cells involved showed the same functional and surface phenotype as displayed by the effectors of the "Winn" assay. It is concluded that in the immune rejection of RSV-induced sarcomas, Lyt-1+, Lyt-2,3+ T cells, rather than cytotoxic T lymphocytes, and lymphokines such as IFN-gamma are involved.

Rous sarcoma virus-induced tumours in mice. II. Contribution of H-2 and non-H-2 alloantigen barriers to tumour immunogenicity in vivo

The features of the immune recognition of a murine fibrosarcoma induced by Rous sarcoma virus were tested in histocompatible and histoincompatible mice. No evidence of a genetic regulation of spontaneous reactivity to tumour-associated antigens was found in various histocompatible F1 hybrids. Incompatibility in multiple minor histocompatibility antigens triggers a host reaction incapable of causing tumour rejection in some cases. The growth rate of incipient tumours is unaffected, whereas that of already visible tumour masses is significantly delayed. Admixture to the challenge of inactivated leukocytes bearing the same minor histocompatibility antigens as the tumour triggers a significantly stronger reaction. The reaction of hosts incompatible in the H-2K or H-2DL regions is quite efficient. However, the intensity of the immune reaction of H-2DLs antigens displayed by tumour cells is markedly dependent on the alleles of genes located in the central regions of the H-2 complex.

Regulation of the macrophage content of neoplasms by chemoattractants

Factor chemotactic for mononuclear phagocytes was found in supernatant fluids of cultured human and mouse tumor cells. In 11 mouse tumors there was a correlation observed between chemotactic activity and macrophage content of neoplastic tissues. Tumor-derived chemoattractants appear to participate in the regulation of tumor-associated macrophages.

Dissection of the antigenic determinants expressed on the cell surface of RSV-transformed fibroblasts by monoclonal antibodies

Fusion of P3/X63-Ag8 mouse myeloma cells with splenocytes obtained from mice hyperimmunized with a BHK hamster fibroblast line transformed by an env-strain of Rous sarcoma virus (RSV) resulted in the production of antibody-secreting hybridomas. Seven hybrid clones secreted antibodies binding to RSV-transformed BHK fibroblasts but not to the parental control non-transformed line. The antibodies produced by three of these clones did identify antigenic determinants expressed also on BHK cells transformed by SV 40. The antibodies produced by four other clones reacted specifically with cells transformed by RSV but not with cells productively infected by the transformation-defective Rous-associated virus-1; one of these reacted with RSV-transformed hamster cells only, three others identified antigenic determinants common to RSV-transformed cells of different animal species. These data give further support to the idea that RSV-transformed cells express a cell-surface antigen, specific for transformation, the expression of which is controlled by the transforming src gene, and that the specificities carried on it follow a complex pattern, arising from the interaction between antigenic determinants of cellular and viral origin.