[Natural killer cells of the lung]

Natural killer cells are lymphocytes which spontaneously destroy tumoral or virus-infected cells in vitro. They are identified on morphological criteria (LGL) and/or on the presence of "surface markers". However, none of these criteria is specific, and they can only be defined by their spontaneous cytolytic activity. These cells, present in numerous organs, have been particularly studied in blood and lymphoid tissue. They intervene in defence mechanisms against virus-infected cells, in the graft-versus-host reaction and in immunosurveillance or tumours. Few studies have been devoted to natural killer cells of the lung. They are present in that organ in the same proportion of lymphocyte population as in blood, but their activity is inhibited by the local microenvironment.