Resistance to cancer exists

In the experiments on the study of tumors usually apply their method of transfer - transplantation from one animal to others. The donor is an animal with a tumor caused by chemical carcinogens or viruses. These studies began on a sound scientific basis only after were withdrawn inbred strains of mice in which animals do not differ genetically from each other. It is easy to understand that when transferring the tumor inside line (it is called syngeneic transplant, or syngeneic transplant tumors) donor tissue does, but for the transplant from a donor other line (allotransplantata) tissue dies. In the latter case, it is obvious difference between animals by antigens of tissue compatibility determining the rejection of both normal and tumor cells, incidentally, explains why cancer is not contagious; at the dawn study antigens a compatible been proven that owing to them, nobody will be able to get cancer under any contact with the case.
Syngeneic transplant tumor seemingly excludes antigenic differences, So it would be quite reasonable to assume that each transplanted clerk will give posterity and all together they quickly form a tumor. However, this "arithmetic" rule was not confirmed. Almost always, in order to cause swelling, you need to migrate from one animal to another... 105 - 107 of tumor cells. If transplanted 10-50 thousand of sick cells, they will die. But in cases not transplantation tumor and normal syngeneic cells they even fewer not perish. The only satisfactory explanation for this difference is that even genetically "identical" tumor cells have some hidden differences from non-tumorous cells, and these differences are recognized by the immune cells of the recipient.
Set: after transplantation animals syngeneic tumor cells most of them (70%to 99%) are killed in the first 4-24 hours, and the latent period of growth for all types of tumor while significantly larger than the estimated (judging from the length of the cycle of division entered cells). From experiments on syngeneic transplant tumors can draw the following conclusions.
1. Detection of tumor cells healthy organism has a specific character, i.e. occurs regardless of the type occurring tumors,
2. The response of the immune system in tumor cells is in the nature of quick (immediate) reaction and requires no prior contact of the body with this tumor antigens. This report is implemented by type of spontaneous cytotoxicity (spontaneously arising hostility lymphocytes against the tumor cells).
The last position is very important, because immunological reaction was divided into immediate reactions associated with development of humoral antibody (e.g. tetanus or diphtheria), and the reaction of the delayed-type, determined by cytotoxic lymphocytes, which arose in the body, not in the first days after antigenic stimulation and later. To them it was decided to include reactions antitumor immunity. It turned out, however, that immunity to tumors related not so much to late arising T-killers, as with the cell of the first line of defence. We are talking about the so-called macrophages and preexisting-killing cells. For the first time the existence of such cells drew the attention of Soviet specialists I. Ya. Chernyakhovsky, E. G. Slavin and G. Ya. Light-Moldovan in 1970. Later, these cells were found in several foreign laboratories. They are called natural killer cells (EC), which reflects their natural origin and biological effect on tumor targets.
And another important consequence arising from experimental observations. We have already mentioned that the success of transplantation depends on the tissue antigens compatibility. Among them is the antigens I and II class. The class I antigens found on the surface membrane of all nuclear cells of the body and are recognized as foreign by allotransplantation. The class II antigens are presented mainly in the cells of the immune system and define the interaction of these cells in the course of the immune response. From the above one can conclude that engraftment syngeneic tumors in animals means their identity by antigen compatibility of the first class.
This obvious conclusion was nevertheless not entirely fair. Often under the influence of carcinogenic factors (physical and chemical products, viruses) composition of the class I antigens changing. If their number decreases, the tumor will immunological recognized, but it will not cause rejection reactions. For the latter you need to tissue donor contain antigens that are missing from the recipient. Such tumors called subimmunogenic. The composition of the class I antigens may due to the activation of normal retarded (repressed) genes to increase, then the tumor become highly immunogenic. Engraftment of such transplanted tumours in animals or the appearance of such spontaneous tumors in people is possible only in case of "escaping" the tumor from under the immune surveillance. On the mechanisms of this process will be discussed below.
The class I antigens in mice (most genetically studied animals) are controlled by approximately 32 genes in humans, their number is much greater. Therefore, their analysis and communication with tumor growth is still largely unexplored. But already obtained a number of important facts. For example, oncologists, on the basis of empirical observations, often not recommend their patients to stay long in the sun or to spend holidays in the South. In the experiment received indicate that UV rays can change the class I antigens and to facilitate the emergence of a rapidly progressing tumors. The peculiarity of these tumors is their ability to "turn off" protection cells of the first defense of the organism - macrophages and the EC. On these data it should be remembered doctors in the appointment of physiotherapeutic procedures in cases of suspected tumor growth.