“…Up to now, NK cells or adequate subsets were found in several tissues of the human body such as lungs, liver, skin, intestine, uterus, bone marrow, spleen, lymph nodes [8], blood, decidua [9], or central nervous system [10]. In bronchoalveolar lavage fluid, macrophages account for more than 80% of total immune cells, while NK cells constitute just around 1% [11]. Even though this hardly suggests a major contribution of NK cells, several studies lay special emphasis on the fact that NK cells still account for 10% of the lymphocytes in the lung, while they additionally show a higher percentage of differentiated/matured cells than in other peripheral organs such as liver, skin and secondary lymphoid tissues.…”