Expression of different lipoprotein receptors in natural killer cells and their effect on natural killer proliferative and cytotoxic activity

Natural killer (NK) cells take up chylomicrons (CM), very low density (VLDL), low density (LDL), high density (HDL) and acetyl-modified low density (AcLDL) lipoproteins through different receptors, VLDL being the lipoprotein with the highest uptake and HDL the lowest. The uptake of LDL can be selectively blocked by the anti-LDL receptor, which does not affect the uptake of CM, VLDL, HDL and AcLDL. Although the uptake of lipoproteins assessed by flow cytometry using DiI is not very high, the lipoproteins are able to induce an increase in proliferative responses, VLDL, AcLDL and HDL being the most important ones with 12- and 17-fold increments, respectively. CM, VLDL and LDL at low concentrations increase NK cytotoxic activity, while HDL and AcLDL inhibit, in a dose-dependent fashion, the killing of NK cells against K562. These results suggest the presence of four different receptors that are responsible for the cytotoxic and proliferative responses observed.     

Effect of eccentric exercise on natural killer cell activity

The effect of eccentric one-legged exercise on natural killer (NK) cell activity was studied in eight healthy males. To distinguish between local and systemic effects, blood samples were collected from veins in the exercising leg and resting arm. However, the results did not significantly differ between the leg and arm. To eliminate diurnal variations, the results were compared with a control group that did not exercise but had blood samples collected at the same time points. In the exercising group, plasma creatine kinase increased progressively during and up to 4 days after exercise. The percentage of CD16+ NK cells increased during exercise, which was paralleled by an increase in the NK cell activity per fixed number of blood mononuclear cells. The NK cell activity on a per NK cell basis did not change. The percentage of CD3+, CD4+, CD8+, CD19+, and CD14+ cells did not change significantly during exercise. The present study thus showed that eccentric exercise with a relatively small muscle mass (1 quadriceps femoris muscle) causes systemic effects on NK cells. It is suggested that the increase in plasma epinephrine during eccentric exercise is responsible for the observed increase in the percentage of CD16+ cells.     

IFN-gamma-inducing factor up-regulates Fas ligand-mediated cytotoxic activity of murine natural killer cell clones

NK cells, non-T non-B immune effector lymphocytes, are localized in many organs, including liver, as well as in the circulation. To investigate the regulatory mechanism of killing apparatus in hepatic NK cells, we established IL-2-dependent NK cell clones from liver lymphocytes of BALB/c nude mice. To generate the NK cell clones, we incubated liver lymphocytes with a high dose of IL-2 in the presence of irradiated Kupffer cells, as feeder cells and as the source of IL-12, originally identified as NK cell stimulatory factor. Unless liver lymphocytes were incubated with both IL-2 and Kupffer cells, no cell growth was observed. Hepatic NK cell clones were established from this cell line by limiting dilution. The surface phenotypes of cloned NK cells were IL-2R beta-chain+ CD16+ CD3- IgM-. The clones did not express NK2.1, which is expressed by a half of NK-enriched spleen cells of BALB/c mice. Although the cells contained dense granules reactive to mAb against perforin, they exerted no conventional cytolytic activity against YAC-1. They constitutively expressed Fas ligand (FasL) and specifically killed Fas-positive target cells by fragmenting DNA. This Fas-FasL-mediated killing activity was enhanced by IFN-gamma-inducing factor, a recently identified novel cytokine produced by activated Kupffer cells, but was not affected by other Kupffer cell-produced cytokines, such as IL-12, IL-1beta, and TNF-alpha. Taken together, these findings suggest that hepatic NK cells participate in the immune response as effector cells through the Fas-FasL system in collaboration with cytokines from Kupffer cells.     

自然杀伤T细胞对小鼠肝癌移植瘤的抑制作用

Objective:The aim of this study was to investigate the inhibition effect of natural killer T (NKT) cells on transplantation hepatocellular carcinoma in mice. Methods:α-galactosylceramide (α-GalCer)-pulsed DC and HepS were prepared as stimulus. Hepatoma xenograft model was established and mice were randomly divided into 4 groups (n = 13 each group):(1)control group, intravenous injection of the same volume of saline. (2) mature DC group, intravenous injection of mature DC cells (4 × 106 cells). (3) α-GalCer-pulsed HepS group, intravenous injection of α-GalCer-pulsed HepS (4 × 106 cells). (4) α-GalCer -pulsed mature DC group, intravenous injection of α-GalCer-pulsed DC (4 × 106 cells). The changes of tumor volume in mice and survival period were measured every 2 days. Percentage of NKT cells in spleens and cytotoxicity of spleen cells were detected by flow cytometry. Tumor tissues were analyzed by histopathological examination. Results:In α-GalCerpulsed Heps and DC groups, the average survival period was prolonged and tumor volume was markedly decreased, spleen cells and NKT cells were significantly increased, and tumor necrosis was evident, compared to the control group. Conclusion:α-GalCer-pulsed DC and HepS could activate NKT cells in vivo, also increase NKT cells cytotoxicity, inhibit the growth of hepatomas and prolong survival period.     

Influence of neuroleptics on cytotoxic activity of macrophages in rats

The aim of the study was to evaluate the influence of neuroleptics on the in vivo and in vitro activities of rat spleen macrophages. In the in vivo study, three neuroleptics (chlorpromazine, haloperidol, and sulpiride) were given once, for 14 or 28 days. In the in vitro study, we evaluated the effects of two different concentrations of the neuroleptics on 3-day cultures of spleen macrophages. Rat spleen macrophages were isolated by the adherence method, and their cytotoxic activity was determined by measuring 51 Cr release from target cells P-815. In the in vitro study, both concentrations of all neuroleptics did not alter the cytotoxic activity of macrophages. In the in vivo study, neuroleptics (chlorpromazine 2 mg/kg, haloperidol 0.5 mg/kg, sulpiride 50 mg/kg) enhanced the cytotoxicity of macrophages both after a single injection and after 14 days. The results of the study indicate that the immunomodulatory effects of the neuroleptics depend mainly on dosage and experimental conditions.     

Inhibition of natural killer cell activity in mice treated with tobacco specific carcinogen NNK

Among the different chemicals present in tobacco and tobacco smoke, 4-(methylnitrosamine)-1-(3-pyridyl)-1-butanone (NNK) is the most potent carcinogen. In the present study the immunosuppressive effect of NNK was investigated in laboratory animals by analyzing the antitumor immune responses. Mice of B6C3F1 strain were treated with different doses of NNK by IP and assayed for natural killer cell activity by the lysis of 51Cr-labeled YAC-1 lymphoma cells. The control mice received physiological saline. The results showed a significant inhibition of natural killer cell activity in the spleen cells of mice treated with 100 or 250 mg/kg NNK. In contrast to the high-dose NNK group, treatment of mice with lower doses of NNK like 10 or 50 mg/kg had no significant effect on the natural killer cell activity. In addition to spleen, the natural killer cell activity was also suppressed in the hilar lymph nodes and lung cells of NNK-treated mice. The clearance of 125I labeled YAC-1 tumor cells was also reduced from the lungs of mice injected with NNK. Further, the metastatic potential of B16F10 melanoma cells was significantly higher, as evidenced by the increased lung tumor nodules in the high-dose NNK-treated mice. The decreased antitumor immune response in the carcinogen-treated mice was not due to a decrease of NK cells, because flow cytometric analysis indicated no change in the frequency of NK 1.1+ cells between control and treated animals. However, there was an increased plasma cortisone levels in the carcinogen-treated mice compared to control animals. Injection of mice with poly I:C or interleukin-12 was able to restore natural killer cell activity in the tobacco carcinogen-treated mice.     

Effect of a Staphylococcus epidermidis-extracted slime factor on human natural killer cell activity

A slime factor produced by Staphylococcus epidermidis was a complex glycoconjugate extracted by the phenol extraction method. The potential stimulatory or inhibitory capacity of the phenol-extracted slime (PES) was tested on human natural killer cell cytotoxic activity. Various concentrations of the PES preparation were incubated with the effector cells 30 min before and during the assay period. The PES factor inhibited natural killer cell cytotoxic activity at a concentration of 250 micrograms/ml and at higher concentrations (p < 0.05). The inhibition of natural killer cell cytotoxic activity may probably be related to the complex composition of the slime substance.     

Direct activity of human T lymphocytes and natural killer cells against Cryptococcus neoformans

Lymphocytes constitute a critical component of host defenses against cryptococcosis. Previously, we demonstrated that human lymphocytes cultured with interleukin-2 formed conjugates with, and directly inhibited the growth of, Cryptococcus neoformans. Here, we explore the anticryptococcal activity of freshly isolated, highly purified populations of human peripheral blood lymphocytes. Lymphocytes were incubated with encapsulated C. neoformans for 24 h, after which the lymphocytes were lysed, dilutions and spread plates were made, and CFU were counted. Fungistasis was determined by comparing growth in wells with and without lymphocytes. Nylon wool-nonadherent peripheral blood mononuclear cells (NWNA PBMC) were highly fungistatic, even if either T cells or natural killer (NK) cells were depleted by panning. A mixed population of T cells and NK cells, obtained by rosetting NWNA PBMC with sheep erythrocytes, completely inhibited cryptococcal growth, whereas the nonrosetting cells had little fungistatic activity. CD4+, CD8+, and CD16/56+ lymphocytes, isolated by positive immunoselection, had potent growth-inhibitory activity. In contrast, purified B cells had no activity. Fungistasis was seen even in the absence of opsonins. Antifungal activity was markedly diminished when surface receptors on NWNA PBMC were cleaved by treatment with trypsin or bromelain. Supernatants from stimulated lymphocytes or concentrated lymphocyte sonicates were not active. Lymphocyte-mediated fungistasis was seen with two different strains of C. neoformans. CD4+, CD8+, and CD16/56+ lymphocytes formed conjugates with C. neoformans, as observed under Nomarski differential interference contrast microscopy and videomicroscopy. These data demonstrate that freshly isolated peripheral blood T cells and NK cells have the capacity to bind and directly inhibit the growth of C. neoformans.     

Lymphopain, a cytotoxic T and natural killer cell-associated cysteine proteinase

Through differential screening of established human leukaemia cell lines, we have identified and molecularly cloned lymphopain, a novel cysteine proteinase of the papain family. Lymphopain exhibits a remarkably restricted cellular pattern of expression, being predominantly expressed in cytotoxic T-lymphocytes and natural killer cells. The human lymphopain locus maps to chromosome 11q13, encodes a polypeptide of 376 amino acids and is conserved in the mouse. Both human and murine forms appear more closely related to protozoan papain-like enzymes than to other mammalian members of the papain family. The cellular distribution of lymphopain expression, together with the functional demonstration of lymphopain-associated proteinase activity in vitro, is suggestive of a role for lymphopain in immune cell-mediated, cell killing.     

Augmentation of natural killer cell activity in mice by oral administration of transforming growth factor-beta

OBJECTIVE: To analyze the effect of HLA-DR genes on susceptibility to and severity of ankylosing spondylitis (AS). METHODS: Three hundred sixty-three white British AS patients were studied; 149 were carefully assessed for a range of clinical manifestations, and disease severity was assessed using a structured questionnaire. Limited HLA class I typing and complete HLA-DR typing were performed using DNA-based methods. HLA data from 13,634 healthy white British bone marrow donors were used for comparison. RESULTS: A significant association between DR1 and AS was found, independent of HLA-B27 (overall odds ratio [OR] 1.4, 95% confidence interval [95% CI] 1.1-1.8, P = 0.02; relative risk [RR] 2.7, 95% CI 1.5-4.8, P = 6 x 10(-4) among homozygotes; RR 2.1, 95% CI 1.5-2.8, P = 5 x 10(-6) among heterozygotes). A large but weakly significant association between DR8 and AS was noted, particularly among DR8 homozygotes (RR 6.8, 95% CI 1.6-29.2, P = 0.01 among homozygotes; RR 1.6, 95% CI 1.0-2.7, P = 0.07 among heterozygotes). A negative association with DR12 (OR 0.22, 95% CI 0.09-0.5, P = 0.001) was noted. HLA-DR7 was associated with younger age at onset of disease (mean age at onset 18 years for DR7-positive patients and 23 years for DR7-negative patients; Z score 3.21, P = 0.001). No other HLA class I or class II associations with disease severity or with different clinical manifestations of AS were found. CONCLUSION: The results of this study suggest that HLA-DR genes may have a weak effect on susceptibility to AS independent of HLA-B27, but do not support suggestions that they affect disease severity or different clinical manifestations.     

Expression of killer cell inhibitory receptors on human uterine natural killer cells

The establishment of the human placenta in early pregnancy is characterized by the presence of large numbers of natural killer (NK) cells within the maternal decidua in close proximity to the fetally-derived invading extravillous trophoblast which expresses at least two HLA class I molecules, HLA-G and HLA-C. These NK cells have an unusual phenotype, CD56(bright) CD16, distinguishing them from adult peripheral blood NK cells. They may control key events in trophoblast migration and therefore placentation. Human NK cells in peripheral blood express receptors for polymorphic HLA class I molecules. This family of receptors, known as killer cell inhibitory receptors (KIR), are expressed on overlapping subsets of NK cells to give an NK cell repertoire which differs between individuals. Using a panel of monoclonal antibodies to several members of the KIR family and analysis by flow cytometry, we have found that KIR are expressed by decidual NK cells. There is variation in both the percentage of cells expressing a particular receptor and the density of receptor expression between decidual NK cells from different individuals. Comparison of NK cells from decidua and peripheral blood of the same individual showed that NK cells from these two different locations express different repertoires of KIR. Receptors are present in individuals who do not possess the relevant class I ligand, raising the possibility that these NK receptors may be involved in recognition of the allogeneic fetus by the mother at the implantation site.     

Phospholipase A2 activity and calpactin I levels in rat lymphokine-activated killer cells: correlation with the cytotoxic activity

The interaction of carnitine with human placental brush-border membrane vesicles was investigated. Carnitine was found to associate with the membrane vesicles in a Na(+)-dependent manner. The time course of this association did not exhibit an overshoot, which is typical of a Na+ gradient-driven transport process. The absolute requirement for Na+ was noticeable whether the association of carnitine with the vesicles was measured with a short time incubation or under equilibrium conditions, indicating Na(+)-dependent binding of carnitine to the human placental brush-border membranes. The binding was saturable and was of a high-affinity type with a dissociation constant of 1.37 +/- 0.03 microM. Anions had little or no influence on the binding process. The binding process was specific for carnitine and its acyl derivatives. Betaine also competed for the binding process, but other structurally related compounds did not. Kinetic analyses revealed that Na+ increased the affinity of the binding process for carnitine and the Na+/carnitine coupling ratio for the binding process was 1. The dissociation constant for the interaction of Na+ with the binding of carnitine was 24 +/- 4 mM. This constitutes the first report on the identification of Na(+)-dependent high-affinity carnitine binding in the plasma membrane of a mammalian cell. Studies with purified rat renal brush-border membrane vesicles demonstrated the presence of Na+ gradient-driven carnitine transport but no Na(+)-dependent carnitine binding in these membrane vesicles. In contrast, purified intestinal brush-border membrane vesicles posses neither Na+ gradient-driven carnitine transport nor Na(+)-dependent carnitine binding.     

Bovine natural killer activity against virally infected cells inhibited by monoclonal antibodies

Forty-four monoclonal antibodies (mAbs) were evaluated for their ability to alter natural killer (NK) cell lysis of virally infected target cells. Six of the mAbs inhibited the lysis of the target cells, while one of the mAbs enhanced lysis. Four of the inhibitory mAbs, CACT26A, CACT16A, CACTB45A and MUC76A, had very marked activity. These mAbs with inhibitory or enhancing activity recognized (1) WC2 molecules (CACTB44A, CACT16A, CACT26A) present on putative NK cells, (2) molecules on granulocytes, monocytes, a subpopulation of lymphocytes (CACTB45A and TH2A), (3) CD11a (MUC76A), and a protein of CD3 (MM1A).     

Decline of natural killer cell target binding and lytic activity in mice exposed to rotation stress.

Examined the effect of rotation-induced stress on (1) the percentage distribution of natural killer (NK) YAC-1 target-binding cells and (2) NK cell activity from splenic lymphocytes of C3H/HeJ mice. Following a 6-day stress regimen, a marked decline in both the percentage of target-binding cells and in NK cell activity was observed. This decline was first evident 13 days after initiation of stress and persisted for 2 wks. Data indicate that intermittent rotation stress over a 6-day period results in a delayed but persistent deleterious effect on NK-YAC-1 target binding and NK cell activity that may be involved in cancer progression of the host. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Activation and cytotoxic activity of macrophages: a short review

Interaction of sensitized T-lymphocytes with specific antigen, as well as several other nonimmunological stimuli, will induce the appearance of new properties in macrophages collectively referred to as "activation". The importance of macrophage activation in various physiological processes is only just beginning to be understood. A growing body of evidence strongly suggests that activated macrophages may play a dual role: firstly in protecting the host against certain interacellular pathogens, and secondly in modulating cell proliferation and adversely affecting cells with abnormal growth properties. It is expected that the ability of activated macrophages to discriminate between normal and tumor cells will receive increasing attention. If confirmed, this property may be of major importance with regard to immunotherapy of tumors.     

Receptors that turn on and turn off natural killer cells

The receptors on natural killer cells for polymorphic major histocompatibility complex or human leukocyte antigen class I molecules have recently been cloned. Two structurally distinct receptor families have been identified from murine and human natural killer cells. These receptors are classified as members of the C-type lectin and immunoglobulin families. Initially, it appeared that murine natural killer cells express the C-type lectin receptors whereas human natural killer cells express immunoglobulin-like receptors. Recent data suggest that human natural killer cells can express both C-type lectin-like receptors and the immunoglobulin-like receptors. The interaction of natural killer-cell receptors with class I molecules was characterized to inhibit natural killer-cell activation; however, allelic forms of these natural killer cell receptors have recently been identified to also have activating properties. These discoveries show the presence of a diversity of receptors for major histocompatibility complex class I molecules on T and natural killer cells. In addition they illustrate the use of two unique strategies by the immune system for eliminating altered- or non-self cells: through the detection of foreign antigens and through the detection of absence of self antigens.     

The basis for self-tolerance of natural killer cells in beta2-microglobulin- and TAP-1- mice

Cells from mice with mutations in the genes for beta2-microglobulin (beta2m) or for TAP-1 express only low levels of MHC class I proteins on their surfaces, and are thus sensitive to attack by normal NK cells. Although NK cells are present in beta2m- mice and TAP-1(-) mice, they are completely self-tolerant. The underlying mechanism for this tolerance is unknown. It has been proposed that education processes render NK cells from these mice hypersensitive to class I-mediated inhibition, so that they can be inhibited even by the low levels of class I expressed on autologous cells. In this study, we present evidence against this hypothesis, by demonstrating that NK cells from beta2m- mice and TAP-1(-) mice fail to attack beta2m(-)TAP-1(-) double-mutant cells in both in vitro and in vivo assays. The latter cells express substantially lower levels of class I than single-mutant cells, based on serologic tests, as well as a significantly diminished sensitivity to attack by class I-specific CTL. Furthermore, the Ly-49 repertoire on NK cells derived from beta2m(-)TAP-1(-) mice is highly similar to that of either single mutant, indicating that the developmental processes that shape the Ly-49 repertoire cannot respond to the differences in class I levels among these mice. We propose that self-tolerance of NK cells in beta2m- mice and TAP-1(-) mice is likely to result from hyporesponsiveness of the cells to activating signals, or alternatively, to induction of inhibitory signaling through receptors specific for non-class I MHC ligands.     

Effect of alpha-tocopherol on the respiratory burst of neutrophils, blast transformation of lymphocytes, and activity of human natural killer cells in blood

The effect of vitamin E on immunological reactions of blood cells was studied. The addition of vitamin E in concentration of 100 microM to neutrophils caused the increase of superoxide production. But this index was decreased when incubation of these cells with A23187 or FMLP was accompanied by alpha-tocopherol in concentration of 100 microM followed by the removal of free ligand or alpha-tocopherol in concentration of 0.5 microM. In the presence of PMA the inhibiting action of alpha-tocopherol was not found (under the 0.5 microM of alpha-tocopherol) or was small (under the concentration of it 100 microM of alpha-tocopherol). The addition of alpha-tocopherol in concentration of 0.5 microM and 50 microM caused the inhibition of blasttransformation of lymphocytes and activity of natural killer cells. This effect was expressed more under the low contents of this vitamin in the incubation medium. The level of blasstransformation of blood in vitamin E-deficient rats was by 20% less than in normal. The exogenous addition of alpha-tocopherol in concentration of 0.5 microM did not affect this value. It was suggested that vitamin E can affect the respiration burst of neutrophils, blasttransformation of lymphocytes and activity of natural killer cells and these actions depend on its concentrations.