An attempt was made to demonstrate an immune reaction as the cause of the spontaneous regression of an autochthonous tumor, the Shope papilloma. It is well known that the incidence of regression is not correlated with antibody titer against the virus responsible for the neoplasm. Therefore, the regression mechanism may be directed specifically against papilloma cells. This hypothesis was tested by attempting to demonstrate anamnestic response in regressor animals upon secondary exposure to autologous papilloma tissue. Papilloma cells were obtained by infecting in short-term organ culture chips of skin, previously washed to free them of antiviral antibody. Papillomas developed from these explants when they were autografted to uninoculated, virus-immune, and papilloma-bearing rabbits. In animals in which papillomas had previously regressed either the papillomas failed to develop or the resultant tumors soon regressed. That the skin from regressor rabbits was fully capable of becoming papillomatous was demonstrated by grafting washed, virus-treated fragments into the cheek pouch of cortisonized hamsters. The results were consistent with the hypothesis that rabbits can develop immunity to autologous papilloma cells. Attempts to transfer this presumptive immune system are in progress.


Supported by Grants CRT-5022 and C-1116 from the National Cancer Institute of the National Institutes of Health, Public Health Service.

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