Studies on the endotoxin induced tumor resistance

Time dependency of endotoxin-induced resistance to transplantable tumors in mice

A single injection of bacterial endotoxin induced cyclic changes of enhanced or reduced host reactivities, as determined in some measurements of the beneficial effects of endotoxin, such as immune potentiation or protection against lethal irradiation. The results described here show that endotoxin-induced resistance to subsequent challenge with transplantable tumors such as Lewis lung carcinoma or L1210 murine leukemia is similarly time dependent. While certain time intervals between endotoxin treatment and tumor challenge will provide significant protection, others will render the recipients highly susceptible to the same tumor. It was also observed that L1210-bearing mice have a lower resistance to endotoxin injections than tumor-free mice of the same strain.

Studies on host defenses enhanced by endotoxins: a brief review

The findings reported here indicate that toxic reactions to endotoxin do not have to be part of the mechanisms leading to clinically improved status of patients or of experimental animals. It seems to be possible to mobilize the host defenses without the unwanted or dangerous side effects which were encountered during fever therapy. For the demonstration of activated host defenses, several experimental models are available. Non-specific resistance to bacterial infections, to lethal irradiation or to experimental challenge with viable tumors are clear manifestations of enhanced capacity of the endotoxin-treated host to compensate for the induced damage, or to cope with an otherwise overwhelming number of pathogenic cells. Immunopotentiation is obviously one of the contributing factors in some of the above parameters. How these results are applicable to human therapy remains to be seen. Such use of endotoxin derivatives, or better, the mediators of beneficial endotoxic effects, must wait until we learn more about the nature of the alternating positive and negative effects of endotoxin application. The importance of the proper timing of such a therapeutic modality cannot be overemphasized.