Apoptosis of tumor cells induced by substances of the circulatory system.

Despite global abnormalities of the immune system, such as in AIDS, the incidence of only a few kinds of tumor increases, and even in the development of these tumors the degree of immunosuppression seems not to be a critical factor. This means that the known immune system has no significant role in the tumor preventing mechanism. Thus, the fact that tumors do not develop in the majority of the population during their lifetime, indicates the existence of an additional defense mechanism of the immune system. We demonstrated previously that this defense is produced by the synergistic action of certain substances of the circulatory system. Here we report that the substances taking part in the defense induced, but only when they were used together, the apoptosis of tumor cells, but not normal cells, as was detected by different methods. Other substances of the circulatory system did not show similar effects. These results further support the existence of the mentioned defense mechanism called by us the Passive Antitumor Defense System.