"Immunologie Surveillance at the Macroscopic Level: Non- selective Elimination of Premalignant Skin Papillomas"

It is now clearly established that many tumors, spontaneous or induced, carry highly potent tumor-specific transplantation antigens (TSTA) which are distinctive from those of the host. Dr. Prehn has carried the evidence for the effect of the immunologie system a little further today in showing, from his studies with Dr. Lappe, that the papilloma, which shares TSTA with the malignant tumor, is susceptible to immunologie control. Nonspecific stimulation of the immune system diminishes the duration of survival of papillomas; depression of the immune system prolongs the survival. In the system he described, the state of immunologie responsiveness appears to affect neither the malignant change itself nor the progression of the malignant tumor. When the existence of TSTA became generally accepted, the most widely accepted hypothesis to explain the failure of the host to reject his own tumor was that he became tolerant to its antigens. This might be because of the extreme slowness of the initial growth and the possibility that at least some TSTA were present in the host at birth or because the tumor outgrew the defense system and overwhelmed it to produce a state analogous with high-dose tolerance. Morton (8) and Weiss et cd. (16) have shown that tolerance to viral antigens can and frequently does develop at birth, and tolerance would, therefore, be expected to a certain (probably large) proportion of virus-induced tumors. Suit and Silobrcic, while failing to show immunity in normal animals (12), could induce immunity in virus-free hybrids but not in reciprocal, viruscarrying hybrids (15). Tolerance does not appear to affect tumors induced in adult life with virus such as the Moloney