Immunological aspects of deoxyribonucleic acid and carcinogenesis

1. LD50 values and 95% confidence limits were determined for the ip route with one strain each o EAT and S-37 tumors. The values obtained were: for EAT 2,000 ± 560; for S-37 45,000 ± 11,866. 2. DNP and DNA were prepared from EAT and S-37 tumors and the prepared material was used for immunization. 3. Mice immunized with DNP prepared from EAT and S-37 and subsequently challenged with viable EAT and S-37 tumor cells showed a considerable degree of resistance as compared to the unimmunized control animals. 4. Cross immunity was demonstrated between mice immunized with DNP from one tumor and challenged with tumor cell other than the type used for immunization. 5. Mice immunized with DNA prepared from EAT and S-37 cells and challenged with viable EAT and S-37 tumor cells showed increased resistance as compared to the unimmunized control animals. The degree of resistance induce using material without the protein moiety was less that that induced by using DNP. 6. Cross immunity was also demonstrated between mice immunized with DNA from one type of tumor cell and then challenged with tumor cells other than the type from which the nucleic acid for immunization was obtained. However, the immunity in this latter circumstance was considerably less than when the immunization carried out with the corresponding DNP. 7. DNP prepared from normal mouse tissue and used for immunization showed no measurable induction of resistance when the mice were tested by challenge with viable tumor cells. 8. Microscopic observation of peritoneal washing from immunized and normal mice that had been challenged with viable tumor cells showed a significantly different cellular and humoral response over a 72-hour period. This response was indicated by lymphocytic and histiocytic infiltration and by lysis of tumor cell.