The first line of defense

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Bred hairless mice, hereditary deprived of the thymus, puzzled researchers; as these mouse resist the development of tumors? It turned out that the absence of these animals T-lymphocytes compensated by the increased number and activity of other cells, natural killer cells (EC). These cells appear in mice after 2-3 weeks after birth, and in the same term of reaching the peak of their activity. Newdow to 6 nedelyu age root and metastasize tumor person, but in adulthood such an effect can be achieved only after irradiation of mice or after the introduction of antibodies to the EC-cells.
Recently experimenters brought a new, so-called "beige" breed mice that have a genetic defect EC. In these mice, there is increased sensitivity to the development of tumors induced by viruses and chemical carcinogens. Thus, at very different experimental models can be traced convincing trend: high activity the EC is associated with resistance to tumor growth, low activity - with weak resistance to cancer.
EC-cells are Autonomous system of lymphocytes that are not dependent on the influences of the thymus. Today it is established that the EC is not homogeneous cells and diverse group of performers cytotoxic functions. The main thing that distinguishes them from other cytotoxic cells (T-killer cells, cytotoxic macrophages, neutrophils), is the ability to kill tumor targets without prior sensitization. EC resistant to gamma rays, they are not disarm even dose to 1000 detrimental to other cytotoxic cells.
Assume that the earliest precursor cell EC can follow one of two paths: either they fall in the thymus and further develop as T-lymphocytes, or pass the thymus and differentiate into T-nezavisimye EC-cells. However, one cannot rule out the possibility of interconversion T - EC-cells, and Vice versa. Introduction of hormones thymus nudam reduces their activity the EC, and removal of the thymus in normal mice increases the number of natural killer cells. The people of the EC represented mainly by large granular lymphocytes with round or kidney-shaped nucleus, expressed chromatin and prominent nucleoli.
In norm the main function of the EC is to destroy normal cells infected with viruses, and tumor cells. The latter is not an end in itself, as the immune system eliminates all the cells with the wrong program development. Therefore, along with the tumor removed and some immature blood-forming elements. In General, the system of cells with spontaneous cytotoxicity was to supervise the emergence of cells with changed order of molecules on the cell membrane. For its part, the function of the EC-cells regulate other cells of the immune system.
As the EC only appear after birth, stimulate their exogenous exposure. A special place among them belongs to viruses. When interactions viruses and cells formed interferon, which is a key regulator of the activity of the EC. It not only promotes the maturation of the EC, but also expands the range of their actions to different targets. EC-cells are activated interleukin-2, which proves the influence on them of T-helpers (see below). Finally, the activation of the EC can also be achieved by mutual cultivation of lymphocytes of different donors. All this makes a General pattern: the function responsible cells in the body is stimulated different, complementary physiological mechanisms.
The more immunogenic tumors, the more sensitive of their cells to cytotoxic damage. This action by the EC on the target cell consists of four main stages: identification killer antigens targets of active multiplication EC, contact with the surface of the target and the actual lysis, or as otherwise it is called, "fatal blow". Two first stages are associated with magnesium ions, two second - with the presence of sodium ions.
The cytotoxic effect of the EC on the target cell can be limited to the damage of a membrane. Such transient ischemic outer membrane of the targets is called embryotoxicity; it may serve as an intermediate stage of a lethal blow. Embryotoxicity and cytotoxicity with irreversible change in the cytoplasm - tools by which the elements of urgent response of the body to provide a finer degree of compliance and adaptation of all cooperating body cells.
In spontaneous tumors, particularly in cancer patients, the activity of the EC usually significantly reduced. The cause of oppression EC serve themselves tumor cells, in particular, this is achieved by products of their factor suppressive EC. In such cases, the cause is not to be confused with the investigation; the weakening of European Commission activities in various kinds of tumors, especially evident in the cases of leukemia, does not contradict the concept of immune surveillance, and reflects the damage to the body's resistance in tumor growth.