NK-Cells: Natural Killers

NK-cells (natural killers) represent a heterogeneous lymphocytes population of innate immune system. They have a natural cytolytic activity, are capable of producing cytokines and chemokines and are involved in the antiviral and antitumor body control. In the quiescent state, an average diameter of NK-cell is about 8.7 microns, while in the moment of its activation it may increase its size up to 10-12 microns (Ferlazzo et al., 2004). This feature was the reason for the initial determination of NK-cells as large granular lymphocytes. NK-cells contain azurophilic granules, which include perforin, granzymes, and other components, with which they carry out contact cytolysis. At different stages of its development, NK-cells express the receptors and a plurality of surface markers that are typical for the cells of myeloid and lymphoid origin, forming a heterogeneous mixture of different subpopulations. NK-cells are widely distributed in the body: they are found in the spleen, liver, peripheral blood, where they number can be up to 9 billion (or 5-20% of the lymphocytes), in a small amount in the lymph nodes and in decidual endometrium. …show more content…
NK-cells are able to eliminate the cells infected with mycoplasma, bacteria, and other pathogens (Caligiuri, 2008). In addition to direct cytolytic activities, natural killer cells have a regulating effect on immune reactions through the secretion of cytokines, chemokines and growth factors. Another important aspect of NK-cells activity in the body is associated with their antitumor activity. At the various types of oncologic diseases, reduced amount of NK-cells activity may serve as prognostic criterion of metastasis, poor response to treatment and decrease in overall survival of cancer patients. Low NK-cells activity may also be a factor of malignant neoplasms