The mechanism of inhibition of alveolar macrophages on autologous blood natural killer cell activity

Histological and biochemical effects of cigarette smoke on lungs

In this study, rats were made to inhale cigarette smoke in a specifically prepared container for different periods. The lung tissue samples of the subjects were examined by light microscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Malonaldehyde, one of the free oxygen radicals was determined in lungs and plasma. The catalase activity level of erythrocyte and arginase levels were determined. Three groups were formed. The rats in the Ist and IInd groups were made to inhale cigarette smoke for 30 and 60 minutes a day for a total period of 3 months. Control group, the rats in the IIIrd group (controls) were made to inhale clean air during the same periods. An increase in the number of macrophages was observed in the pulmonary tissue of the exposed groups. Especially in the group that inhaled the smoke for long periods, the number of macrophages and the inclusion bodies contained in them increased. These differences could easily be observed in TEM studies. In the light microscopy and SEM observations, it arouse attention that the alveolar macrophages occurred as sets and their activation increased. Depending on the length of the exposure to cigarette smoke, an increase in the number of macrophages was observed. Statistically significant increases were determined in the malonaldehyde levels of pulmonary tissue and plasma when compared to the control group. Besides significant increases were found in the catalase activity levels of erythrocytes in the experimental groups.

Possible role and mechanism of inactivation of decidual NK cells in pregnancy

Decidual NK cells are present in murine decidua in early pregnancy, but they decline by midpregnancy. The participation of these cells in rapid rejection of abnormal fetuses and possible cytolitic activity of these cells to trophoblasts seems unlikely. But, their production of cytokines (like CSF-1, which promote differentiation and growth of trophoblasts cells) may be the primary role of decidual NK cells in time of establishment of fetal-maternal connection. Later, inactivation of decidual NK cells by prostaglandins prevents damage of embryos.

Alveolar macrophage inhibition of lung-associated NK activity: involvement of prostaglandins and transforming growth factor-beta 1

Natural killer (NK) activity plays an important role in host defense. It is likely that this defensive role is shaped by compartmental and local environmental factors. The present study investigated the regulatory effects of alveolar macrophages (AM) on lung-associated NK activity. AM and lung lymphocytes (LL) were permitted to interact in a two-chamber system which prohibited cell contact but supported diffusion of soluble factors. AM were found to inhibit NK activity from LL in a time-dependent and reversible manner. The inhibitory event was shown to be mediated by soluble factors acting upon a post-binding event(s) in the lytic pathway of LL. AM inhibition was sensitive to indomethacin treatment (10(-5) M), which caused a decrease in prostaglandin E2 (PGE2) concentrations. Quantitation of PGE2 levels and treatment of LL with exogenous PGE2 indicated that the inhibitory effect could not be exclusively due to PGE2. It was subsequently found that exogenous transforming growth factor-beta 1 (TGF-beta 1) also inhibited LL NK activity and that treatment of inhibitory AM supernatant with a neutralizing antibody to TGF-beta 1 adsorbs up to 55% of its inhibitory activity. Moreover, the amount of TGF-beta 1 found in AM-LL co-culture media (25 pg/mL) correlated well with the level of NK inhibition observed. By contrast, platelet-derived growth factor and nitric oxide did not play a significant role in mediating AM suppression. Taken together, the data suggest that AM inhibit lung NK activity by interfering with post-binding lytic event(s) through the production of PGE2 and TGF-beta 1.

Natural killer activity is present in rat lung lavage and inhibited by lidocaine

Natural killer (NK) cells play an important role in defense against tumors and certain infected cells. Although NK activity is present in cells recovered from lung parenchyma, its demonstration in cells retrieved from normal bronchoalveolar lavage (lung lavage) has been difficult. In this study, we report that NK cells are present and active in normal rat lung lavage. Purified effector cells retrieved from lung lavage and peripheral blood mononuclear cells were compared for NK activity. NK activity was tested in a four hour 51-chromium release assay against radiolabeled Yac-1 target cells and expressed as lytic units (LU). There was no difference in NK activity between the blood and lung (80 +/- 10 LU vs. 62 +/- 15 LU). Since lidocaine is used in lung lavage for topical anaesthesia in humans and to increase the cell yield in animals, we also sought to determine if it could affect NK activity. We found that lidocaine inhibited NK activity in a dose dependent manner when it was instilled into the airways prior to performance of lavage. Lidocaine did not affect the yield of cells recovered from lavage, their relative proportions, nor their viability. Lung macrophages (93 +/- 1% nonspecific esterase positive) inhibited blood NK activity, an effect significantly augmented by lidocaine. In sum, we report that NK activity in lung lavage is similar to that found in blood and may be regulated by alveolar macrophages and that topical lidocaine inhibits NK activity, an effect which needs to be considered in studies of these cells from lung lavage.