Abstract
gamma-Irradiated rat hepatoma cells are immunogenic in syngeneic WAB/Not rats, so that immunized animals are protected against tumour-cell challenge and circulating tumour-specific antibody is produced. Treatment of the immunizing cells with glutaraldehyde at concentrations of 0.001% or greater for 30 min rendered these cells non-protective in tumour-rejection tests and no longer able to induce significant formation of specific antibody. However, tumour-specific antigens were shown to be expressed upon treated cells; they specifically bound tumour-specific antibody from syngeneic immune sera assessed in indirect membrane-immunofluorescence tests. Also, these cells specifically absorbed antibody from immune or tumour-bearer sera, as demonstrated in the indirect membrane-immunofluorescence test or a complement-dependent 51Cr-release test. Alloantigen expression was not influenced by glutaraldehyde treatment, although glutaraldehyde-treated hepatoma cells failed to induce alloantibody formation in KX/Not rats. Polyacrylamide-gel electrophoresis of treated cells, surface-labelled with 125I, indicated that extensive cross-linking of the surface protein occurred as a result of glutaraldehyde treatment. The present findings establish that although the expression of a tumour-specific antigen is necessary for the induction of immuno-protection against tumour-cell challenge, this alone is not a sufficient condition for eliciting tumour immunity.
Highlights
Summary.-y-irradiated rat hepatoma cells are immunogenic in syngeneic WAB/ Not rats, so that immunized animals are protected against tumour-cell challenge and circulating tumour-specific antibody is produced
THE ATTENUATION of tumour cells by chemical treatment before using them as immunogens has been considered attractive from several viewpoints (Prager & Baechtel, 1973; Sanderson & Frost, 1974; Staab & Anderer, 1977), since previous studies have indicated that immunization with chemically modified antigens, such as flagellin, results in enhanced cell-mediated immunity and depressed antibody responses (e.g. Parish & Liew, 1972)
These results suggest that the activity of the tumour-specific antigen associated with D23 is lost or significantly diminished when assayed by the induction of immune responses, the results in Table IV indicate that glutaraldehyde-treated y-irradiated D23 cells still retain a serologically identifiable tumour-specific antigen when assessed in membrane-immunofluorescence tests
Summary
It may be further argued that, by presenting an animal with a chemically attenuated tumour cell, the reactivity against tumourassociated antigens may be enhanced by responses against new determinants introduced by the chemical modification This notion has been supported by experimental evidence ever since Landsteiner (1945) demonstrated that antibodies induced by immunization with conjugated protein had a broad range of specificities. BALDWIN surface of an aminoazodye-induced rat hepatoma (D23) have been investigated This tumour is characterized by the expression of a tumour-specific rejection antigen against which it is possible to induce moderate levels of immunoprotection when y-irradiated tumour cells are used as immunogen (Baldwin & Barker, 1967a; Price et al, 1978). Y-irradiated hepatoma cells as an immunogen of defined efficacy were treated with glutaraldehyde at various concentrations and their immunogenicity and expression of surface antigens were evaluated
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