Agglutinating Antibodies in the Sera of Chickens with Regressing Rous Sarcomas

Abstract

SEVERAL antigens specific for tumour cells have been identified^1–7 in tumours induced by viruses, and virus-induced resistance to tumour cell antigens has been established^8–11. It now seems important to investigate surface tumour cell antigens because they may be involved in the induction of resistance. I have studied the surface cell antigens of chicken sarcomas induced by the Rous virus (Carr–Zilber strain), using sera from adult chickens in which tumours, induced by the virus or by transplanted tumour cells, had regressed after an initial period of active growth. Regression was most frequent in chickens inoculated with low doses of virus or tumour cells. The sera were heated at 56° C for 30 min and added to a cell suspension prepared from chicken Rous sarcoma. The suspension contained 2 × 10⁷ cells/ml. Sera taken from intact healthy chickens were used as a control. The mixtures of cells and immune or control sera were kept at 4° C for 18 h. The reaction was checked under the microscope (magnification × 120). Table 1 shows that of thirteen sera taken from chickens in which the tumours had regressed, nine produced agglutination of tumour cells (Fig. 1). Sera from fifteen control chickens and twenty-five chickens with actively growing sarcomas showed no agglutinating activity. Agglutinating antibodies appeared in the blood at the time of tumour regression arid remained there in some cases for a period of 60–105 days after regression. Our stock of chickens was not inbred so it was necessary to find whether immune sera would also agglutinate normal chicken cells. Sera were therefore added to a cell suspension prepared from the spleen, liver, thymus and bursa of Fabricius of untreated chickens. Immune sera also agglutinated normal chicken cells. These results show that the antibodies, or at least some of them, were isoantibodies directed against the isoantigens of tumour and normal tissue.