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It was shown by agglutination, gel diffusion, and immunoelectrophoretic tests that an antigen common toMycobacterium bovis (BCG) and some malignant and normal cells of rat tissues exists. By absorption of immune sera and the agglutination test the specificity of this antigen was demonstrated for BCG cells and cells of primary induced tumors of rat muscle tissue. This antigen has electrophoretic mobility in the β-globulin zone.

The sera of Wistar and noninbred rats of different ages and sexes were found to contain an extremely thermostable factor, resistant to various chemicals, which inhibits the action of normal and immune antibodies against the red blood cells and serum antigens of rats. The blocking factor is relatively species specific and is more active in respect of the action of normal than of immune antibodies. The activity of the blocking factor is connected with α1-globulin.

Agglutination, gel precipitation and immunoelectrophoresis demonstrated the presence of antigens common for human malignant tumors of different sites and BCG and Listeria monocytogenic microorganisms. The radioimmunoassay of sera in the agglutination test showed that these sera reacted with tumor cells rather than with cells from normal human tissues. The common antigen had the electrophorectic mobility in the beta-globulin zone.

Thermostable antigens (TA) were found by the gel precipitation test and by immunoelectrophoresis in malignant tumors of muscle tissue induced by dimethylbenzanthracene, and in the amniotic fluid of 8–12-day embryos and certain normal organs of adult Wistar rats. Relative tissue specificity of these antigens was demonstrated, on the one hand, for tumors, amniotic fluid, and the uterus, and on the other hand for the lung, spleen, and serum. TA detected in tumors and amniotic fluid by immunoelectrophoresis are located in the zones of α- and α1-globulins.

Serums with a comparatively high titer of immune antibodies were obtained in immunization of rabbits by ascitic cells of malignant tumors (Ehrlich's adenocarcinoma of mice and Iosida's sarcoma of rats). Serums with lower titers of immune antibodies were recovered in immunization of rabbits by the water-salt extracts of the tissue of subcutaneous forms of tumors. Serums of the first, as well as of the second type are not very specific: they react in comparatively high titers with the antigens from the tumor tissues and with those from the tissues of normal organs of the laboratory animals.

Metastasis of transplantable malignant tumors is a complicated process in which the localization of the primary tumor and its biological peculiarities together with other factors play an important role. Guerin rat's carcinoma, which metastasizes into internal organs both in subcutaneous inoculation and in its graft into the testicle or into the abdominal cavity, was found to be the most suitable for the study of the laws of metastasis of malignant tumors. Rat's M-1 sarcoma and Y oshida's sarcoma arethe least suitable for the study of this process.

Sarcoma M-1, as a rule, produces no metastases when inoculated subcutaneously in rats. Metastases develop in the abdominal cavity of experimental animals when this tumor is inoculated into the testicle. Decrease of malignancy is noted in metastatic tumor on the surface of the diaphragm and is manifested in reduced percentage of positive inoculations and in prolonged latent period in subcutaneous inoculation of the tissue from the metastatic tumors in rats.

The explants of a Brown-Pearce rabbit carcinoma cultured on human serum and heterogenic embryonic and yeast extract, show growth in a number of cases, when mixed with fresh undiluted human serum and transplanted intratesticularly in rabbits; later they regress.

Sera of rabbits, immunized with water-salt extract from the tissue of Guerin's carcinoma and normal rat erythrocytes, react with the antigens of the tumor tissue, the uterus; kidney, and erythrocytes. This points to the presence of a common antigen in these tissues and erythrocytes. It is possible to extract (to a considerable extent) antigens common to the erythrocyte antigens from the water-salt extract of tumor tissue by means of antierythrocytic serum in the presence of the guinea pig serum complement. Antigens, common to the tissue of a homologous normal organ (uterus), are retained in such an exhausted extract. These data show that at least two types of antigens are present in the tumor tissue (along with other antigens) i.e., species and tissue ones. The commoness of antigenic properties of Guerin's carcinoma, normal uterus, kidney tissue, and erythrocytes were also demonstrated by the tissue culture method.

Normal tissue antibodies contained in the sera of normal rabbits and reacting to extracts from their own organs are destroyed when heated to 65° during 30 min; antibodies detected in the sera of immune rabbits and reacting to antigens from the tissue of their own organs are resistant to this temperature. The sera of rabbits immunized with heterogeneous organ tissue exhibit clear-cut precipitation lines (up to 2 lines) in gel with antigens from the tissue of the rabbit's own kidney.

Gel precipitation and immunoelectrophoresis have demonstrated the presence of thermostable tumour-associated antigens in blood serum from tumour-bearing rats and culture supernatant of malignant cells. These antigens have the electrophoretic mobility in the zones of beta-, alpha- and alpha 1-globulins.

A complete inhibition of the tumor growth (100%) is observed following transplantation of the skin in rabbits 8 days before inoculation of Brown-Pearce metastasis of tumors following simultaneous skin transplantation and inoculation of Brown-Pearce carcinoma. Transplantation of the skin 8 days after tumor inoculation caused intensified growth of Brown-Pearce carcinoma, manifested in the greater percentage of positive takes and a more vigorous metastasization.

An extremely thermostable and resistant to some chemical substances factor was found in the sera of Wistar and noninbred rats of different age, male and female. This factor inhibited the action of normal and immune antibodies to rat erythrocytes and rat serum antigens. The blocking factor was relatively specific and more effective in respect to the normal antibodies than to the immune ones. The activity of the blocking factor was connected with the alpha1-globulin.

As a result of the complex immunobiological study in an autologous system on the models of DMBA induced tumors in muscular tissue there were shown 3 types of cell response to primary tumors, their metastases and autotransplantation: no response, moderate and very pronounced reaction. In a definite percentage of cases autologous peritoneal macrophages were found to inhibit malignant cells in autotransplantation. The percentage of positive inoculations and an average weight of transplants of primary tumors and their metastases at the moment of highest transplantation immunity (12-14 days) have been definitely correlated with the intensity of cell response developed in these tissue, and also are dependent on individual features of proper malignant cells.

Gel precipitation and immunoelectrophoresis have demonstrated the presence of thermostable tumour-associated antigens in blood serum from tumour-bearing rats and culture supernatant of malignant cells. These antigens have the electrophoretic mobility in the zones of beta-, alpha- and alpha 1-globulins.

Agglutination, gel precipitation and immunoelectrophoresis tests demonstrated the presence of antigens common for the Mycobacterium bovis (BCG) and some malignant and normal rat tissue cells. The method of absorption of immune sera in the agglutination test showed that this antigen was specific for the BCG microorganisms and cells of primary induced tumours of rat muscle tissue. This antigen had the electrophoretic mobility in the beta-globulin zone.

Gel precipitation and immunoelectrophoresis tests tests demonstrated the presence of thermostable antigens in dimethylbenzanthracene-induced malignant tumours of the muscle tissues of Wistar rats. These antigens were relatively tissue-specific for the tumours, amniotic fluid and the uterus on the one hand, and for the lung, spleen, and the serum on the other hand. The thermostable antigens of the tumours and the amniotic fluid had the electrophoretic mobility in the zone of alpha and alpha1-globulins.

In two immunological reactions (immunocytoadherence and inhibition of macrophage adherence in the presence of specific antigens) it was shown that autologous and homologous native sera in some percentage of cases render an inhibitory effect. One of the blocking factors of sera proved to be rather thermostable, the other, on the contrary, to be thermolable.