Lung Natural Killer Cell Activity Research Articles

FHL2 Regulates Natural Killer Cell Development and Activation during Streptococcus pneumoniae Infection.

Recent in silico studies suggested that the transcription cofactor LIM-only protein FHL2 is a major transcriptional regulator of mouse natural killer (NK) cells. However, the expression and role of FHL2 in NK cell biology are unknown. Here, we confirm that FHL2 is expressed in both mouse and human NK cells. Using FHL2−/− mice, we found that FHL2 controls NK cell development in the bone marrow and maturation in peripheral organs. To evaluate the importance of FHL2 in NK cell activation, FHL2−/− mice were infected with Streptococcus pneumoniae. FHL2−/− mice are highly susceptible to this infection. The activation of lung NK cells is altered in FHL2−/− mice, leading to decreased IFNγ production and a loss of control of bacterial burden. Collectively, our data reveal that FHL2 is a new transcription cofactor implicated in NK cell development and activation during pulmonary bacterial infection.

Differential lung NK cell responses in avian influenza virus infected chickens correlate with pathogenicity.

Infection of chickens with low pathogenicity avian influenza (LPAI) virus results in mild clinical signs while infection with highly pathogenic avian influenza (HPAI) viruses causes death of the birds within 36–48 hours. Since natural killer (NK) cells have been shown to play an important role in influenza-specific immunity, we hypothesise that NK cells are involved in this difference in pathogenicity. To investigate this, the role of chicken NK-cells in LPAI virus infection was studied. Next activation of lung NK cells upon HPAI virus infection was analysed. Infection with a H9N2 LPAI virus resulted in the presence of viral RNA in the lungs which coincided with enhanced activation of lung NK cells. The presence of H5N1 viruses, measured by detection of viral RNA, did not induce activation of lung NK cells. This suggests that decreased NK-cell activation may be one of the mechanisms associated with the enhanced pathogenicity of H5N1 viruses.

Rapid NK-cell activation in chicken after infection with infectious bronchitis virus M41

Natural killer (NK) cells are cytotoxic lymphocytes and play an important role in the early defence against viruses. In this study we focussed on NK cell and interferon (IFN) responses after infection with infectious bronchitis virus (IBV). Based on surface expression of CD107+, enhanced activation of lung NK cells was observed at 1dpi, whereas in blood prolonged NK-cell activation was found. IFN-α and IFN-β mRNA and proteins were not rapidly induced whereas IFN-γ production in lung, measured by Elispot assay, increased over time at 2 and 4dpi. In contrast, IFN-γ production in blood was highest at 1dpi and decreased over time down to levels comparable to uninfected birds at 4dpi. Collectively, infection with IBV-M41 resulted in activation of NK cells in the lung and blood and rapid production of IFN-γ and not IFN-α and IFN-β compared to uninfected birds.

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

Natural killer (NK) cells have a specialized function in peripheral organs, which is determined by the organ-specific niches. We have attempted to explore whether lung NK cells display a particular phenotype according to their function in the unique pulmonary environment in health or during respiratory infection in mice. In healthy mice, higher frequencies of NK cells among lymphocytes were detected in the lung than in other tissues (lymph node, bone marrow, spleen, blood and liver), and lung NK cells maintained a more mature phenotype, implying that lung NK cells were critical for the pulmonary immune response. However, lung NK cells expressed higher levels of inhibitory receptors and lower levels of activating receptors, migration/adhesion-associated molecules and co-stimulatory molecules than splenic NK cells, implying that lung NK cells were quiescent, and the activation of lung NK cells was tightly regulated by the pulmonary environment in health. During respiratory infection, lung NK cells could be activated and express functional molecules (CD107a and interferon-γ) to take part in the response to infection quickly. These results suggested that the unique pulmonary environment promotes the development of NK cells with a lung-specific phenotype.

Inhibition of Lung Natural Killer Cell Activity by Smoking: The Role of Alveolar Macrophages

Background: It is known that natural killer (NK) cell activity in the lung of smokers (SM) is lower than in non-smokers (NS). However, little is known about the underlying mechanisms. Objective: The purpose of this work was to investigate the mechanisms of the inhibition of NK cell activity by alveolar macrophages (AM) in SM. Methods: Lung effector cells and AM were obtained using bronchoalveolar lavage. The NK cell activity was assayed by ⁵¹Cr release method after incubation of 4 and 24 h, using K562 as target cell. AM were added at a concentration of 25% to effector cells. Results: Following 24-hour culture, NK cell activity significantly increased in the NS but not in the SM. Lung NK cell activity was significantly augmented by interleukin-2 in the NS but not in the SM. Addition of AM to the NK cell preparation from SM exerted a significantly greater suppressive effect on autologous blood NK cell activity than in the NS. Indomethacin, catalase or thiourea did not prevent AM-mediated suppression of NK cell activity, in contrast to superoxide dismutase. Conclusions: These results suggest that the suppression of NK cell activity by AM in SM may be caused by O^–₂ release rather than by prostaglandins, H₂O₂ or OH release from AM.

Construction of a double recombinant adenovirus vector expressing a heterodimeric cytokine: in vitro and in vivo production of biologically active interleukin-12.

Interleukin-12 (IL-12) is a heterodimeric cytokine that plays an important role in the development of cellular immunity. Clinical applications for this lymphokine include resolution of infectious disease, cancer immunotherapy, and boosting cellular immunity in AIDS patients. When using IL-12 and other cytokines therapeutically, an approach designed to obtain localized cytokine expression would be beneficial, because this could reduce the problem of systemic toxicity. As a means of developing a suitable delivery vehicle for IL-12, we have produced double-recombinant adenovirus vectors containing the p35 subunit cDNA of murine IL-12 in early region 1 of adenovirus type 5 and the cDNA for p40 in early region 3 (AdmIL-12). Cell lines infected with AdmIL-12 produced up to 42,000 units of IL-12/10(6) cells per 24 hr. Biological activity of the virally expressed product was demonstrated in vitro through its ability to induce proliferation of phytohemagglutinin (PHA)-stimulated lymphoblasts and to stimulate natural killer (NK) activity in naive splenocytes. Mice injected intraperitoneally with these vectors displayed serum IL-12 levels that increased proportionately with the amount of virus administered. IL-12 production in vivo caused a dose-dependent increase in splenic and lung NK cell activity. This work represents the first demonstration of a double-recombinant adenovirus vector expressing a functional heterodimeric protein. The results of these studies support the use of AdmIL-12 as an efficient delivery vehicle for IL-12, and direct studies of its ability to modulate cellular immunity in vivo are currently underway.

Enhancement of pulmonary natural killer cell activity by platelet activating factor. Mechanisms of activation involving Ca2+, protein kinase C, and lipooxygenase products.

The modulation of lung natural killer (NK) cell activity by platelet-activating factor (PAF) and the mechanisms underlying this regulation were examined. When rat lung large granular lymphocytes (LGL) were cultured with PAF we observed an elevation of NK cell activity in a concentration-dependent fashion. Peak effect was observed at 10(-9) M PAF. Kinetic studies indicated that this enhancement occurred when effector cells were preincubated with PAF for 18 h as well as for shorter times. Inhibition of protein synthesis by cycloheximide blocked the PAF-enhanced NK cell activity after preincubation for 18 h. Extracellular Ca2+ was also needed for the action of PAF as suggested by the effects of Ca2+ chelation with ethyleneglycol-bis-(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) and inhibition of Ca2+ entry into the cells with verapamil and diltiazem, all of which abrogated the action of PAF. Furthermore, the enhancement of cytotoxicity was blocked by specific PAF receptor antagonists BN 52021, BN 52111, and WEB 2086. The mechanism of activation appeared to involve protein kinase C (PKC) since pretreatment of lung LGL with the PKC inhibitors H-7 or staurosporine abrogated the PAF-induced effect. Inhibition of 5-lipoxygenase by AA-861 inhibited partially the PAF-induced augmentation of NK cell activity, suggesting an implication of endogenous leukotrienes (LT) in this system. In parallel, addition of exogenous LTB4 to lung LGL stimulated their NK cell activity but to a lower level comparatively with PAF. Taken together, our studies indicate that PAF can significantly augment lung NK cell activity and that this effect is dependent on PKC, 5-lipoxygenase, and extracellular calcium.

Enhancement of Pulmonary Metastases Induced by Decreased Lung Natural Killer Cell Activity

Administration of repeated high doses of 7.5 mg chlorozotocin [(CZT) CAS: 54749-90-5]/kg to syngeneic WAG rats bearing the rhabdomyosarcoma 9-4/0 enhanced the incidence of spontaneous metastasis compared to its incidence in untreated rats. This enhancement was observed concomitantly with an increase in the survival of 9-4/0 rhabdomyosarcoma and P 77 fibrohistiocytoma tumor cells, labeled with [125I]5-iodo-2'-deoxyuridine or 51Cr and injected iv. Within the first 24 hours after P 77 cell injection, the lungs retained 10% of the cells while the lungs of controls or of rats given one CZT injection only retained 0.06%. The natural killer (NK) cell cytotoxicity of cells flushed out from lung capillaries [lung intracapillary cells (LIC)] was studied concomitantly in a 4-hour 51Cr release assa against YAC-1 and P 77 target cells. A large reduction was again observed in NK cytotoxicity but only after repeated injections of 7.5 mg CZT/kg. Lung defenses were gradually restored after treatment stopped. Administration of polyinosinic-polycytidylic acid with CZT restored the NK cell cytotoxicity of LIC and inhibited lung metastases amplification. The close relationship between metastasis and NK activity indicates the need for caution as regards the effects of chemotherapy on NK activity.

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

The lung is affected by disorders in which natural killer (NK) cells are thought to play an important defensive role. This study, however, demonstrated that normal lung lymphocytes actually express very little NK cell activity (P less than 0.001 compared with blood lymphocytes). This was true independent of the NK-sensitive target used (K562, U937, MOLT-3, or Daudi). This lack of lung lymphocyte NK activity occurred even though the proportions of lymphocytes in the normal lower respiratory tract with the morphology (large granular lymphocytes) and surface antigen markers of NK cells were similar to that of blood (P greater than 0.5). Although normal lung lymphocytes bound to known NK-sensitive targets, they did not lyse these cells (P less than 0.001 compared with blood), which suggested that the lack of lung NK cell activity resulted from a relative inability of lung NK cells to destroy their targets. While the mechanisms of this functional impotence of lung NK cells are not clear, normal human alveolar macrophages and lower respiratory tract epithelial lining fluid exerted a profound suppressive effect on blood NK cell activity (P less than 0.001 for both) by inhibiting their ability to lyse target cells after binding (P less than 0.001). Though impotent initially, when incubated for 24 h in medium alone, normal lung lymphocytes demonstrated markedly enhanced NK activity (P less than 0.02), which suggested that lung NK cells do have the potential to express NK activity. Interleukin-2 (IL-2) further augmented this effect (P less than 0.05), but gamma interferon did not (P greater than 0.2). Consistent with this observation, lung lymphocytes from patients with active sarcoidosis, a disease in which lung lymphocytes are spontaneously releasing IL-2, did express NK cell activity (P less than 0.01). These studies suggest that although NK cells are present in the normal lung, they are functionally inactive, due, at least in part, to local inhibitory influences. In the presence of IL-2, however, lung NK cell activity is expressed, which suggests that lung NK cell activity can be modulated.