Natural killer cells are present in the normal human lung but are functionally impotent.

Increased numbers of T lymphocytes with gamma delta-positive antigen receptors in a subgroup of individuals with pulmonary sarcoidosis.

“…In regards to sarcoidosis, this is consistent with the observation ofcells with increased natural killer-like activity in lung and blood of sarcoid individuals (79)(80)(81). Thus, it is plausible that the natural killer-like function may be associated with at least part of the exaggerated y6+ T cell numbers observed in this subgroup of individuals with sarcoid.…”

Lung natural killer cells in mice: phenotype and response to respiratory infection

“…Some studies have shown that the functions of NK cells from bronchoalveolar lavage fluid and lung tissue are suppressed. 24 In our study, when compared with NK cells from any other tissues, lung NK cells expressed higher levels of inhibitory receptors and lower levels of activating receptors, which also indicated that the activation of lung NK cells may need to overcome a higher threshold of inhibition. Alveolar macrophages that can produce interleukin-10 and transforming growth factor-b to restrain the inflammatory response in the lung may be responsible for this inhibitory effect on the activation of lung NK cells.…”

“…Some studies have shown that lung NK cells have lower cytotoxic capacity than blood NK cells. 9,24 In our study, the number of NK cells in the lung was increased after infection with respiratory pathogen. Previous studies have demonstrated that, within days or hours of infection, NK cells are recruited into the lung from the peripheral blood and become activated to secrete cytokines.…”

Gamma interferon is spontaneously released by alveolar macrophages and lung T lymphocytes in patients with pulmonary sarcoidosis.

“…In this context, in active pulmonary sarcoidosis, lung T lymphocytes are spontaneously releasing monocyte chemotactic factor (12) and IL-2 (13, 14) and provide nonspecific polyclonal help to B cells (15). Further, lung lymphocytes from patients with active sarcoidosis demonstrate exaggerated natural killer cell activity (16), an observation consistent with heightened local immune processes. Mononuclear phagocytes from the lung of sarcoid patients also appear activated, in that they demonstrate an enhanced ability to present antigen to autologous T lymphocytes (17) and are spontaneously releasing fibronectin (18) and the alveolar macrophage-derived growth 1.…”