DMBA induced papillomas in congenitally athymic (nude) and hereditarily asplenic (Dh/+) mice: contrasts and comparisons with immunologically intact littermates.

Congenitally athymic (nude) and hereditarily asplenic (Dh/+) mice were painted with dimethylbenzanthracene (DMBA) to compare skin tumor development in these immunodeficient animals with their immunologically normal littermate controls. Papillomas were induced in all groups of mice. However, nude and Dh/+ mice were significantly more resistant than their normal littermates to tumor induction. Furthermore, the number of papillomas/mouse and the total tumor incidence were significantly greater in control mice and the latency period for tumor appearance was shorter and the tumor growth rate greater in normal mice compared to their immunodeficient littermates. Finally, nu/+ skin transplanted to nude mice and then painted with DMBA behaved in similar fashion as nude skin. These findings, when discussed in terms of target organs for DMBA, suggest a major role for the immune system in stimulating papilloma induction.