The author's research interest started with a Shwartzman-type hemorrhagic necrosis reaction caused by interaction of bacterial components and natural antibodies 1). This interest recently led to success in inducing Shwartzman-type necrosis in a mass of Ehrlich solid carcinoma and subsequent reduction and resolution of the mass with a high success rate 2). At the same time, we also learned that intensive immunization of mice with aerobic and anaerobic bacteria components does not interfere with engraftment of Ehrlich carcinoma cells. Ehrlich carcinoma cells were successfully transplanted into inflammatory lesions induced by bacterial components, suggesting that neither immune response to bacterial components nor inflammatory lesions cause necrosis of Ehrlich carcinoma cells or interfere with their engraftment. Interestingly, mice in which Ehrlich carcinoma cells resolved following the aforementioned procedure remained stubbornly resistant to the second transplantation of these cells 3). Subcutaneous rechallenge of Ehrlich carcinoma cells into these mice resulted in coagulative necrosis of the carcinoma tissue. In addition to reactions in transplantation sites, systemic reactions, particularly those affecting blood vessels such as plasma-cell response, were also induced. Immune responses likely to be associated with hyperimmunity were also induced in the spleen and lymph nodes. Mice resistant to Ehrlich carcinoma transplants were also resistant to transplantation of sarcoma 180 and skin isografts, as well as to rechallenging with Ehrlich carcinoma. Such immunity can be transferred to isogeneic mice via serum or skin transplantation, but not by lymphocytes. This appears to be mediated by heat-sensitive components of serum, although no antibody has been identified in vitro. Meanwhile, this immunity is not transferred to next-generation progeny 3, 4).
The transplantation immunity was found to be of low-level specificity and humorally mediated. We also proposed that "development" and "bearing" of carcinoma should be considered separate issues, as we do for issues of "infection" and "symptom onset" 5). Apart from the issue of carcinoma development, if immunological issues regarding carcinomas and carcinoma-bearing animals are regarded as part of the issues related to tissue transplantation, namely, isogeneic transplantation (e.g., carcinoma transplantation between laboratory animals) and autologous transplantation (e.g., development of idiopathic carcinoma), immunological studies on isogeneic or autologous transplantation are actually linked to studies on cancer treatment. The current major focus is on how to improve engraftment of tissue and organ transplants. If immunological issues between carcinomas and carcinoma-bearing animals are regarded as an aspect of tissue transplantation-related issues, and if observation is made through the aforementioned procedure, then the first step of the spread of nonspecific necrosis to a carcinoma mass and subsequent necrosis of carcinoma tissue seems to differ mechanistically from the second step in which anti-transplant immunity is established, as if transplantation immunity of low-level specificity is acquired by the animal. This might partially explain why research on the anti-tumor effect of bacterial components, an interesting research subject with a long history, has not progressed smoothly. If this speculation is correct, and if it is possible to mimic exclusively the mechanism of the second step, then it is likely that the same outcome can be obtained more easily by omitting the first step. On the basis of the results of the above-mentioned studies and incidental results obtained in our previous studies on intractable cutaneous ulcer 6), we have successfully induced anti-transplant immunity to carcinoma transplants in mice by administering gelatin and gelatin derivatives with methylene-polymerized amino groups.

Methods and results

Merck gelatin, bone gelatin, bovine bone gelatin, 2 types of bovine skin gelatin, 2 types of porcine skin gelatin, 2 types of porcine gelatin, whale gelatin, whale brain gelatin, collagen, crude collagen and Merck gelatin with methylene-polymerized amino groups were used. The gelatin products were dissolved in water to make a 1% solution, and 0.3 ml of each solution was subcutaneously injected into the inguinal region of mice 3 times at a 1-week interval. Seven days after the last injection, 5 x 106 Ehrlich carcinoma cells were transplanted subcutaneously into the lumbar area.
The results are summarized in Table 1. For mice in which carcinoma cells did not engraft after a 1-month observation, the same number of carcinoma cells were again subcutaneously transplanted to confirm that the cells were not accepted in these mice. Different types of gelatin showed different degrees of effect; porcine gelatin was the most effective while whale gelatin was the least effective. Methylene-polymerization of the amino groups resulted in an enhanced effect of gelatin. These mice were found to have the same immunological characteristics as the anti-transplant immunity acquired by using bacterial components, as described above. In addition, administration of gelatinase failed to substitute the effects of the gelatin products.

This abstract was presented at the 20th Annual Meeting of Japanese Society of Allergology.