The role of natural killer cells in histoplasmosis

The natural killer (NK) cell has been suggested as an early defense mechanism against Histoplasma capsulatum. Homozygous bg/bg mice, heterozygous bg/+ mice, and bg/+ mice treated with anti-asialo GM1 (ASGM1) were used to assess this postulated role. NK cell assays demonstrated that ASGM1 was effective in reduction of NK cell activity in bg/+ mice to levels comparable to bg/bg mice. To test for possible cross reaction with other immune cells and ASGM1, we evaluated lymphocyte and macrophage function. These studies included lymphocyte transformation, delayed-type hypersensitivity (DTH), and macrophage candidacidal activity. We found no evidence of any effects from ASGM1. Mice were evaluated for survival and colony counts after intravenous (i.v.) H. capsulatum challenge. We again confirmed increased susceptibility of bg/bg mice to H. capsulatum, but found no significant differences between bg/+ mice and bg/+ mice treated with ASGM1. Therefore, we conclude that NK cells play no major role in nonspecific early host defenses against H. capsulatum.     

Mycobacterial infection in natural killer T cell knockout mice

To gain a better understanding of the pathological role of natural killer (NK) T cells in murine tuberculosis, NKT knockout (KO) mice (J(alpha)281(-/-)mice) were utilized. Eight-week-old NKT KO mice of BALB/c origin and wild-type (WT) mice were infected with Mycobacterium tuberculosis Kurono strain by the airborne route using an airborne infection apparatus, and their capacity to control mycobacterial growth, granuloma formation, and cytokine production were examined. The NKT KO mice developed granulomatous lesions in the lungs; there was no statistically significant difference in pulmonary granuloma size between NKT KO and WT mice (p<0.01). The average CFU values increased 3 weeks post-infection, but decreased 9 and 11 weeks post-infection, in the lungs of NKT KO mice. When stimulated with Kurono strain in vitro, splenic cells from NKT KO mice produced less IFN-gamma than did those from WT mice. Expression of mRNA for IL-2, IL-4, IL-6, IL-10 and IL-12 p40 was slightly lower in NKT KO mice compared with WT mice. Our data indicate that NKT cells play a detrimental role in late-phase mycobacterial infection, although Th1 cells are essential in early-phase mycobacterial infection.     

Alterations in natural killer cells and natural killer T cells during acute viral hepatitis E

The mechanism of liver damage in acute hepatitis E is poorly understood. In this study, we assessed the frequency and activation status of natural killer (NK) and natural killer T (NKT) cells and cytotoxic activity of NK cells in the peripheral blood mononuclear cells (PBMCs) obtained from patients with hepatitis E (n = 41) and healthy controls (n = 61). Flow cytometry was used to assess NK (CD3(-)/CD56(+)) and NKT cell (CD3(+)/CD56(+)) fractions (% of PBMCs) and activation status (CD69(+); % of NK, NKT cells). NK cell cytotoxicity was assessed using major histocompatibilities complex-deficient K562 cells as target cells. In 14 patients, the studies were repeated during the convalescence period. Patients had fewer median (range) NK cells [8.9% (2.4-47.0) vs 11.2% (2.6-35.4)] and NKT cells [8.7% (2.8-34.1) vs 13.6% (2.3-36.9)] than controls (P < 0.05 each). Activation markers were present on large proportion of NK cells [43.5% (11.2-58.6) vs 15.5% (3.0-55.8)] and NKT cells [41.5% (17.4-71.1) vs 12.8% (3.3-63.2); P < 0.05 each] from patients. NK cell cytotoxicity was similar in patients and controls. During convalescence, all the parameters normalized. In conclusion, reversible alterations in NK and NKT cell number and activation status during acute hepatitis E suggest a role of these cells in the pathogenesis of this disease.     

Pathogenic role of natural killer T and natural killer cells in acetaminophen-induced liver injury in mice is dependent on the presence of dimethyl sulfoxide

Dimethyl sulfoxide (DMSO) is commonly used in biological studies to dissolve drugs and enzyme inhibitors with low solubility. Although DMSO is generally thought of as being relatively inert, it can induce biological effects that are often overlooked. An example that highlights this potential problem is found in a recent report demonstrating a pathogenic role for natural killer T (NKT) and natural killer (NK) cells in acetaminophen-induced liver injury (AILI) in C57Bl/6 mice in which DMSO was used to facilitate acetaminophen (APAP) dissolution. We report that NKT and NK cells do not play a pathologic role in AILI in C57Bl/6 mice in the absence of DMSO. Although AILI was significantly attenuated in mice depleted of NKT and NK cells prior to APAP treatment in the presence of DMSO, no such effect was observed when APAP was dissolved in saline. Because of this unexpected finding, the effects of DMSO on hepatic NKT and NK cells were subsequently investigated. When given alone, DMSO activated hepatic NKT and NK cells in vivo as evidenced by increased NKT cell numbers and higher intracellular levels of the cytotoxic effector molecules interferon-gamma (IFN-gamma) and granzyme B in both cell types. Similarly, when used as a solvent for APAP, DMSO again increased NKT cell numbers and induced IFN-gamma and granzyme B expression in both cell types. CONCLUSION: These data demonstrate a previously unappreciated effect of DMSO on hepatic NKT and NK cells, suggesting that DMSO should be used cautiously in experiments involving these cells.     

The immune response to primary EBV infection: a role for natural killer cells

The role of antigen-specific CD3(+)CD8(+) cytotoxic T cells in the control of primary Epstein-Barr Virus (EBV) infection is well established. However, time is required for the antigen-specific immune response to develop and expand. In contrast, innate immune responses, such as natural killer (NK) cells, are considered vital early in the infection process. We analysed the scale, phenotype and function of the NK cell response during symptomatic primary EBV infection, infectious mononucleosis (IM) and showed that NK cell numbers were significantly elevated both at diagnosis of IM and in the first month following diagnosis. There were also significant changes in cell phenotype and function, an increase in the proportion of CD56(bright) cells at diagnosis, and freshly isolated cells showing an enhanced ability to kill EBV-infected cell lines. Moreover, in our cohort of IM patients higher NK cell counts were associated with significantly lower viral load in peripheral blood. Our results suggest NK cells have an important role in the control of primary EBV infection by eliminating infected B cells and augmenting the antigen-specific T cell response via release of immunomodulatory cytokines. The magnitude of the NK cell response may ultimately determine whether primary EBV infection has a clinical outcome.     

Emerging role of uterine natural killer cells in establishing pregnancy

Normal pregnancy has been considered as a controlled state of inflammation at an early stage of blastocyst implantation that subsequently develops systemically. Till recent past most popular hypotheses regarding status of immune system in pregnancy were dominated by the Th1 and Th2 hypothesis, in which the fetus avoids maternal rejection through a bias towards T-helper (Th2) cytokine production. Recent findings have shown that predominant immune interactions in the human deciduas are between the placental trophoblast and maternal uterine natural killer (uNK) cells rather than the T cells. Thus NK cells are emerging as important players in the uterine immune response to invasive forms of placenta, as in cases of hemochorial placenta. In humans there is a lack of evidence for T-cell responses to trophoblast cells; therefore it was thought that uterine NK cells are the key factors by which the maternal immune system recognizes trophoblast cells. In this review we are trying to summarize the role of uNK cells in the maintenance of normal pregnancy in humans.     

伯氏疟原虫对小鼠脾B细胞和自然杀伤细胞及其表面分子的影响

为探讨伯氏疟原虫对小鼠脾B细胞和自然杀伤(NK)细胞及其表面分子的影响,将10只雌性C57BL/6小鼠随机分为健康对照组和感染组,每组5只。感染组小鼠经尾静脉注射伯氏疟原虫(106个/鼠)进行感染,健康对照组注射等量生理盐水。感染后6 d,取小鼠脾,制备单细胞悬液,采用流式细胞术检测小鼠B细胞和NK细胞的含量及其表面分子CD62L、CXCR3、CD69的表达水平。结果显示,感染组小鼠脾B细胞百分比含量为(79.2±3.6)%,高于健康对照组的(54.3±4.4)%(P<0.01);感染组脾NK细胞百分比为(2.2±0.7)%,低于健康对照组的(4.6±0.8)%(P<0.01)。CD62L在感染组B细胞中的百分比为(77.7±4.4)%,高于健康对照组的(72.8±7.1)%,但二者差异无统计学意义(P>0.05);CD62L在感染组NK细胞中的百分比为(61.9±4.8)%,低于健康对照组的(86.6±4.2)%(P<0.01)。CXCR3在感染组B细胞中的百分比为(4.1±0.1)%,高于健康对照组的(3.0±0.2)%(P<0.01);CXCR3在感染组NK细胞中的百分比为(2.1±0.9)%,低于健康对照组的(2.3±0.4)%,但二者差异无统计学意义(P>0.05)。CD69在感染组B细胞和NK细胞中的百分比分别为(54.3±4.7)%、(22.2±1.6)%,均高于健康对照组的(1.9±0.4)%、(1.3±0.3)%(P<0.01)。提示感染疟原虫的小鼠可能通过增加B细胞的数量以及上调其表面分子CXCR3和CD69及NK细胞表面分子CD69的表达水平发挥抗疟作用。     

Toll-like receptor 2 mediates fatal immunopathology in mice during treatment of secondary pneumococcal pneumonia following influenza

Host inflammatory responses contribute to the significant immunopathology that occurs during treatment of secondary bacterial pneumonia following influenza. We undertook the present study to determine the mechanisms underlying disparate outcomes in a mouse model with β-lactam and macrolide antibiotics. Lysis of superinfecting bacteria by ampicillin caused an extensive influx of neutrophils into the lungs resulting in a consolidative pneumonia, necrotic lung damage, and significant mortality. This was mediated through Toll-like receptor (TLR) 2 and was independent of TLR4 and the Streptococcus pneumoniae cytotoxin pneumolysin. Treatment with azithromycin prevented neutrophil accumulation and rescued mice from subsequent mortality. This effect was independent of the antibacterial activity of this macrolide since dual therapy with ampicillin and azithromycin against an azithromycin-resistant strain also was able to cure secondary pneumonia. These data suggest that strategies for eliminating bacteria without lysis coupled with immunomodulation of inflammation should be pursued clinically.     

Natural killer cells and natural killer T cells

NK cells are important in protecting against viral infections, and they may regulate the immune response. They are activated by hematopoietic blasts and pose a barrier to bone marrow transplantation. They are also abundant in the pregnant uterine decidua, although their role there is unknown. NK cells are normally inhibited from responding to host cells by inhibitory receptors that recognize self class I MHC antigens. There is evidence that NK cells may be important in the regulation of autoimmunity, but there is even stronger evidence that NKT cells regulate autoimmunity. The mechanisms by which these cells are activated and by which they regulate other cells are now being understood at the molecular level.     

The dynamic changes of circulating invariant natural killer T cells during chronic hepatitis B virus infection

Aim

The protective role of invariant natural killer T cells (iNKTs) against hepatitis B virus (HBV) infection remains controversial. We sought to clarify the role of peripheral iNKT cells during chronic HBV infection.

Methods

Sixty patients with chronic HBV infection were categorized into an immune tolerance phase (HBV-IT) (n = 16), an immune clearance phase (HBV-IC) (n = 19) and an inactive carrier phase (HBV-IA) (n = 25). Twenty healthy individuals were enrolled as healthy controls. Another 21 HBeAg-positive patients were administrated with entecavir (0.5 mg/day) for 6 months. The percentages of circulating iNKT cells and their IFN-γ and IL-4 expression levels were examined by flow cytometry. The relationships between serum HBV DNA, ALT levels, the percentages of iNKT cells, and their IFN-γ and IL-4 levels were analyzed.

Results

Compared to healthy controls, the percentage of iNKT cells decreased in HBV-IT, but increased in HBV-IC and HBV-IA. Circulating IFN-γ-producing iNKT cells gradually increased, whereas IL-4-producing iNKT cells gradually decreased from HBV-IT stage to HBV-IC and HBV-IA stages. The frequency of iNKT cells and their IFN-γ levels were reversely correlated with viral load. The levels of IL-4 expressed by iNKT cells were positively correlated to viral load and the serum ALT levels. After anti-virus therapy, the percentage of IFN-γ-producing iNKT cells increased while the percentage of IL-4-producing iNKT cells decreased.

Conclusions

During chronic HBV infection, the percentages of peripheral iNKT cells and its cytokines expressions of IFN-γ and IL-4 showed dynamic changes. The expression levels of IFN-γ and IL-4 were correlated with the clearance of HBV and liver injury.

     

Human natural killer cells

Natural killer (NK) cells were discovered more than 30 years ago. NK cells are large granular lymphocytes that belong to the innate immune system because unlike T or B lymphocytes of the adaptive or antigen-specific immune system, NK cells do not rearrange T-cell receptor or immunoglobulin genes from their germline configuration. During the past 2 decades there has been a substantial gain in our understanding of what and how NK-cells "see," lending important insights into their functions and purpose in normal immune surveillance. The most recent discoveries in NK-cell receptor biology have fueled translational research that has led to remarkable results in treating human malignancy.     

Arylsulfatase in natural killer cells: its possible role in cytotoxicity.

Ultrastructural cytochemistry of natural killer cells enriched by Percoll gradient centrifugation showed them to possess arylsulfatase (aryl-sulfate sulfohydrolase, EC 3.1.6.1). The enzyme was located in vesicles, granules, and the parallel tubular arrays, organelles characteristic for cytotoxic lymphocytes. Biochemically, peak enzyme activity correlated with the Percoll fractions containing cells with cytotoxicity for melanoma target cells. Treatment of natural killer cells with Na2SO4, a competitive inhibitor of arylsulfatase, suppressed cytotoxicity by almost 50%. Electron microscopy of effector-target cell conjugates, which had been permitted to incubate for only 30 min, disclosed numerous arylsulfatase-positive sites at the points of contact between the effector/target cell membranes. Thus, the enzyme was translocated to the surface before lysis of the target cell was morphologically evident. It is postulated that the parallel tubular arrays play a role in this translocation and that arylsulfatase may function in the degradation of cerebroside sulfate ester components of the target cell membrane to initiate the lytic event.     

In vivo natural killer cell activities revealed by natural killer cell-deficient mice

Studies of natural killer (NK) cell function in vivo have been challenging primarily due to the lack of animal models in which NK cells are genetically and selectively deficient. Here, we describe a transgenic mouse with defective natural killing and selective deficiency in NK1.1(+) CD3(-) cells. Despite functionally normal B, T, and NK/T cells, transgenic mice displayed impaired acute in vivo rejection of tumor cells. Adoptive transfer experiments confirmed that NK1.1(+) CD3(-) cells were responsible for acute tumor rejection, establishing the relationship of NK1.1(+) CD3(-) cells to NK cells. Additional studies provided evidence that (i) NK cells play an important role in suppressing tumor metastasis and outgrowth; (ii) NK cells are major producers of IFNgamma in response to bacterial endotoxin but not to interleukin-12, and; (iii) NK cells are not essential for humoral responses to T cell-independent type 2 antigen or the generalized Shwartzman reaction, both of which were previously proposed to involve NK cells.     

自然杀伤细胞在丙型肝炎病毒感染过程中发挥重要作用

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