| Popis: |
NK cells represent a lymphoid subpopulation which is able to lyse certain tumor cells, virally infected cells, as well as blasts without prior sensibilisation or immunization. Originally, NK cell were characterized solely on their cytotoxic function as no surface markers for identification of these cells were available [1]. It could be demonstrated that NK cells are of large size and contain densely staining cytoplasmic azurophilic granules which coined them the designation “large granular lymphocytes” [2] However, it soon became apparent that NK cells could not be assigned to any known lymphocyte linage. The phenotyping of immune cells by means of mAb classified NK cells as a lymphoid subpopulation that does not express T cell receptors or surface immunoglobulins and which is characterized by the CD3- CD16+CD56+ surface phenotype [3] Further surface proteins typically found on NK cells are: CD2, CD11, CD25, CD54, CD57, and CD58 [4] Although NK-cells were initially identified in human peripheral blood where they make up to 5% of all lymphatic cells, they are also found in the spleen, lung intestinum, intestinal mucosa, liver sinusoid, and peritoneal cavity [5]. Recent data have substantially modified the general concept that NK cells lyse target cells in a non-MHC-restricted function since it has been shown that NK cells are capable of discriminating among different normal allogenic target cells. There is evidence that, at least in some instances, molecules recognized by NK cells are encoded by HLA class I genes expressed on target cells. |
