A non-x-linked syndrome with susceptibility to severe Epstein-Barr virus infections

Bioinformatics Approach to Identify Significant Biomarkers, Drug Targets Shared Between Parkinson's Disease and Bipolar Disorder: A Pilot Study

Parkinson’s disease (PD) is a neurodegenerative disorder responsible for shaking, rigidity, and trouble in walking and patients’ coordination ability and physical stability deteriorate day by day. Bipolar disorder (BD) is a psychiatric disorder which is the reason behind extreme shiftiness in mood, and frequent mood inversion may reach too high called mania. People with BD have a greater chance of developing PD during the follow-up period. A lot of work has been done to understand the key factors for developing these 2 diseases. But the molecular functionalities that trigger the development of PD in people with BD are not clear yet. In our study, we are intended to identify the molecular biomarkers and pathways shared between BD and PD. We have investigated the RNA-Seq gene expression data sets of PD and BD. A total of 45 common unique genes (32 up-regulated and 13 down-regulated) abnormally expressed in both PD and BD were identified by applying statistical methods on the GEO data sets. Gene ontology (GO) and BioCarta, KEGG, and Reactome pathways analysis of these 45 common dysregulated genes identified numerous altered molecular pathways such as mineral absorption, Epstein-Barr virus infection, HTLV-I infection, antigen processing, and presentation. Analysis of protein-protein interactions revealed 9 significant hub-proteins, namely RPL21, RPL34, CKS2, B2M, TNFRSF10A, DTX2, HLA-B, ATP2A3, and TAPBP. Significant transcription factors (IRF8, SPI1, RUNX1, and FOXA1) and posttranscriptional regulator microRNAs (hsa-miR-491-3p and hsa-miR-1246) are also found by analyzing gene-transcription factors and gene-miRNAs interactions, respectively. Protein-drug interaction analysis revealed hub-protein B2M’s interaction with molecular drug candidates like N-formylmethionine, 3-indolebutyric acid, and doxycycline. Finally, a link between pathological processes of PD and BD is identified at transcriptional level. This study may help us to predict the development of PD among the people suffering from BD and gives some clue to understand significant pathological mechanisms.

Innate Immune Response Against HIV-1

The innate immune system is comprised of both cellular and humoral players that recognise and eradicate invading pathogens. Therefore, the interplay between retroviruses and innate immunity has emerged as an important component of viral pathogenesis. HIV-1 infection in humans that results in hematologic abnormalities and immune suppression is well represented by changes in the CD4/CD8 T cell ratio and consequent cell death causing CD4 lymphopenia. The innate immune responses by mucosal barriers such as complement, DCs, macrophages, and NK cells as well as cytokine/chemokine profiles attain great importance in acute HIV-1 infection, and thus, prevent mucosal capture and transmission of HIV-1. Conversely, HIV-1 has evolved to overcome innate immune responses through RNA-mediated rapid mutations, pathogen-associated molecular patterns (PAMPs) modification, down-regulation of NK cell activity and complement receptors, resulting in increased secretion of inflammatory factors. Consequently, epithelial tissues lining up female reproductive tract express innate immune sensors including anti-microbial peptides responsible for forming primary barriers and have displayed an effective potent anti-HIV activity during phase I/II clinical trials.

How I Manage Natural Killer Cell Deficiency

Natural killer (NK) cell deficiency (NKD) is a subset of primary immunodeficiency disorders (PID) in which an abnormality of NK cells represents a major immunological defect resulting in the patient’s clinical immunodeficiency. This is distinct from a much larger group of PIDs that include an NK cell abnormality as a minor component of the immunodeficiency. Patients with NKD most frequently have atypical consequences of herpesviral infections. There are now 6 genes that have been ascribed to causing NKD, some exclusively and others that also cause other known immunodeficiencies. This list has grown in recent years and as such the mechanistic and molecular clarity around what defines an NKD is an emerging and important field of research. Continued increased clarity will allow for more rational approaches to the patients themselves from a therapeutic standpoint. Having evaluated numerous individuals for NKD, I share my perspective on approaching the diagnosis and managing these patients.

Natural Killer Cell Therapy: A New Treatment Paradigm for Solid Tumors

In treatments of solid tumors, adoptive transfer of ex vivo expanded natural killer (NK) cells has dawned as a new paradigm. Compared with cytotoxic T lymphocytes, NK cells take a unique position targeting tumor cells that evade the host immune surveillance by down-regulating self-antigen presentation. Recent findings highlighted that NK cells can even target cancer stem cells. The efficacy of allogeneic NK cells has been widely investigated in the treatment of hematologic malignancies. In solid tumors, both autologous and allogeneic NK cells have demonstrated potential efficacy. In allogeneic NK cell therapy, the mismatch between the killer cell immunoglobulin-like receptor (KIR) and human leukocyte antigen (HLA) can be harnessed to increase the antitumor activity. However, the allogeneic NK cells cause more adverse events and can be rejected by the host immune system after repeated injections. In this regard, the autologous NK cell therapy is safer. This article reviews the published results of clinical trials and discusses strategies to enhance the efficacy of the NK cell therapy. The difference in immunophenotype of the ex vivo expanded NK cells resulted from different culture methods may affect the final efficacy. Furthermore, currently available standard anticancer therapy, molecularly targeted agents, and checkpoint inhibitors may directly or indirectly enhance the efficacy of NK cell therapy. A recent study discovered that NK cell specific genetic defects are closely associated with the tumor immune microenvironment that determines clinical outcomes. This finding warrants future investigations to find the implication of NK cell specific genetic defects in cancer development and treatment, and NK cell deficiency syndrome should be revisited to enhance our understanding. Overall, it is clear that NK cell therapy is safe and promises a new paradigm for the treatment of solid tumors.

From the "missing self" hypothesis to adaptive NK cells: Insights of NK cell-mediated effector functions in immune surveillance

The original discovery of NK cells approximately 40 yr ago was based on their unique capability to kill tumor cells without prior sensitization or priming, a process named natural cytotoxicity. Since then, several studies have documented that NK cells can kill hematopoietic and nonhematopoietic cancer cells. NK cells also recognize and kill cells that have undergone viral infections. Besides natural cytotoxicity, NK cells are also major effectors of antibody-dependent cell cytotoxicity (ADCC). Therefore, NK cells are well "armed" to recognize and mount immune responses against "insults" that result from cell transformation and viral infections. Because of these attributes, an essential role of NK cells in tumor surveillance was noted. Indeed, several studies have shown a correlation between impaired NK cell cytotoxicity and a higher risk of developing cancer. This evidence led to the idea that cancer initiation and progress is intimately related to an abnormal or misdirected immune response. Whereas all these ideas remain current, it is also true that NK cells represent a heterogeneous population with different abilities to secrete cytokines and to mediate cytotoxic functions. In addition, recent data has shown that NK cells are prone to suffer epigenetic modifications resulting in the acquisition of previously unrecognized attributes such as memory and long-term survival. Such NK cells, referred as "adaptive" or "memory-like," also display effector functions that are not necessarily equal to those observed in conventional NK cells. Given the new evidence available, it is essential to discuss the conceptual reasoning and misconceptions regarding the role of NK cells in immune surveillance and immunotherapy.

Emerging insights into human health and NK cell biology from the study of NK cell deficiencies

Human NK cells are innate immune effectors that play a critical roles in the control of viral infection and malignancy. The importance of their homeostasis and function can be demonstrated by the study of patients with primary immunodeficiencies (PIDs), which are part of the family of diseases known as inborn defects of immunity. While NK cells are affected in many PIDs in ways that may contribute to a patient's clinical phenotype, a small number of PIDs have an NK cell abnormality as their major immunological defect. These PIDs can be collectively referred to as NK cell deficiency (NKD) disorders and include effects upon NK cell numbers, subsets, and/or functions. The clinical impact of NKD can be severe including fatal viral infection, with particular susceptibility to herpesviral infections, such as cytomegalovirus, varicella zoster virus, and Epstein-Barr virus. While NKD is rare, studies of these diseases are important for defining specific requirements for human NK cell development and homeostasis. New themes in NK cell biology are emerging through the study of both known and novel NKD, particularly those affecting cell cycle and DNA damage repair, as well as broader PIDs having substantive impact upon NK cells. In addition, the discovery of NKD that affects other innate lymphoid cell (ILC) subsets opens new doors for better understanding the relationship between conventional NK cells and other ILC subsets. Here, we describe the biology underlying human NKD, particularly in the context of new insights into innate immune cell function, including a discussion of recently described NKD with accompanying effects on ILC subsets. Given the impact of these disorders upon human immunity with a common focus upon NK cells, the unifying message of a critical role for NK cells in human host defense singularly emerges.

HHV-6A/6B Infection of NK Cells Modulates the Expression of miRNAs and Transcription Factors Potentially Associated to Impaired NK Activity

Natural killer (NK) cells have a critical role in controlling virus infections, and viruses have evolved several mechanisms to escape NK cell functions. In particular, Human herpesvirus 6 (HHV-6) is associated with diseases characterized by immune dysregulation and has been reported to infect NK cells. We recently found that HHV-6 in vitro infection of human thyroid follicular epithelial cells and T-lymphocytes modulates several miRNAs associated with alterations in immune response. Since miRNAs are key regulators of many immune pathways, including NK cell functions, we aimed to study the impact of HHV-6A and -6B in vitro infection on the intracellular mediators correlated to NK cell function. To this purpose, a human NK cell line (NK-92) was infected in vitro with HHV-6A or 6B and analyzed for alterations in the expression of miRNAs and transcription factors. The results showed that both viruses establish lytic replication in NK-92 cells, as shown by the presence of viral DNA, expression of lytic transcripts and antigens, and by the induction of an evident cytopathic effect. Notably, both viruses, although with species-specific differences, induced significant modifications in miRNA expression of miRNAs known for their role in NK cell development, maturation and effector functions (miR-146, miR-155, miR-181, miR-223), and on at least 13 miRNAs with recognized role in inflammation and autoimmunity. Also the expression of transcription factors was significantly modified by HHV-6A/6B infection, with an early increase of ATF3, JUN and FOXA2 by both species, whereas HHV-6A specifically induced a 15-fold decrease of POU2AF1, and HHV-6B an increase of FOXO1 and a decrease of ESR1. Overall, our data show that HHV-6A and -6B infections have a remarkable effect on the expression of miRNAs and transcription factors, which might be important in the induction of NK cell function impairment, virus escape strategies and related pathologies.

NK Cells in HIV Disease

Natural killer (NK) cells play a critical role in viral immunity. In the setting of HIV infection, epidemiologic and functional evidence support a role for NK cells in both protection from new infection and in viral control. Specifically, NK cells directly mediate immune pressure leading to virus evolution, and NK cell receptor genotypic profiles, clonal repertoires, and functional capacity have all been implicated in virus containment. In addition, indirect NK cell-mediated antibody-dependent cellular cytotoxicity has been linked to vaccine-induced protective immunity against HIV infection. With recent advances in our understanding of NK cell deficiency, development, memory-like responses, and editing of the adaptive immune system, the opportunities to direct and exploit NK cell antiviral immunity to target HIV have exponentially grown. In this review, we seek to highlight the intersections between discoveries in basic NK cell biology and the challenges of HIV chronic infection, vaccine development, and cure/eradication strategies.

Genetic Causes of Human NK Cell Deficiency and Their Effect on NK Cell Subsets

Human NK cells play critical roles in human host defense, particularly the control of viral infection and malignancy, and patients with congenital immunodeficiency affecting NK cell function or number can suffer from severe illness. The importance of NK cell function is particularly underscored in patients with primary immunodeficiency in which NK cells are the primary or sole affected population (NK cell deficiency, NKD). While NKD may lead to the absence of NK cells, we are also gaining an increasing appreciation of the effect that NKD may have on the generation of specific NK cell subsets. In turn, this leads to improved insights into the requirements for human NK cell subset generation, as well as their importance in immune homeostasis. The presence of inherently abnormally developed or functionally impaired NK cells, in particular, appears to be problematic in the way of interfering with normal human host defense and may be more impactful than low numbers of NK cells alone. Here, we review the known genetic causes of NKD and the insight that is derived by these into the requirements for human subset generation and, by extension, for NK cell-mediated immunity.

Biallelic mutations in IRF8 impair human NK cell maturation and function

Human NK cell deficiencies are rare yet result in severe and often fatal disease, particularly as a result of viral susceptibility. NK cells develop from hematopoietic stem cells, and few monogenic errors that specifically interrupt NK cell development have been reported. Here we have described biallelic mutations in IRF8, which encodes an interferon regulatory factor, as a cause of familial NK cell deficiency that results in fatal and severe viral disease. Compound heterozygous or homozygous mutations in IRF8 in 3 unrelated families resulted in a paucity of mature CD56dim NK cells and an increase in the frequency of the immature CD56bright NK cells, and this impairment in terminal maturation was also observed in Irf8-/-, but not Irf8+/-, mice. We then determined that impaired maturation was NK cell intrinsic, and gene expression analysis of human NK cell developmental subsets showed that multiple genes were dysregulated by IRF8 mutation. The phenotype was accompanied by deficient NK cell function and was stable over time. Together, these data indicate that human NK cells require IRF8 for development and functional maturation and that dysregulation of this function results in severe human disease, thereby emphasizing a critical role for NK cells in human antiviral defense.

Activation of protein kinase C and protein kinase D in human natural killer cells: effects of tributyltin, dibutyltin, and tetrabromobisphenol A

Up to now, the ability of target cells to activate protein kinase C (PKC) and protein kinase D (PKD) (which is often a downstream target of PKC) has not been examined in natural killer (NK) lymphocytes. Here we examined whether exposure of human NK cells to lysis sensitive tumor cells activated PKC and PKD. The results of these studies show for the first time that activation of PKC and PKD occurs in response to target cell binding to NK cells. Exposure of NK cells to K562 tumor cells for 10 and 30 min increased phosphorylation/activation of both PKC and PKD by roughly 2-fold. Butyltins (tributyltin (TBT), dibutyltin (DBT)) and brominated compounds (tetrabromobisphenol A (TBBPA)) are environmental contaminants that are found in human blood. Exposures of NK cells to TBT, DBT, or TBBPA decrease NK cell lytic function in part by activating the mitogen-activated protein kinases (MAPKs) that are part of the NK lytic pathway. We established that PKC and PKD are part of the lytic pathway upstream of MAPKs and thus we investigated whether DBT, TBT, and TBBPA exposures activated PKC and PKD. TBT-activated PKC by 2-3-folds at 10 min at concentrations ranging from 50 to 300 nM while DBT caused a 1.3-fold activation at 2.5 µM at 10 min. Both TBT and DBT caused an approximately 2-fold increase in phosphorylation/activation of PKC. Exposures to TBBPA caused no statistically significant changes in either PKC or PKD activation.

Brominated flame retardants, tetrabromobisphenol A and hexabromocyclododecane, activate mitogen-activated protein kinases (MAPKs) in human natural killer cells

Natural killer (NK) cells provide a vital surveillance against virally infected cells, tumor cells, and antibody-coated cells through the release of cytolytic mediators and gamma interferon (IFN-γ). Hexabromocyclododecane (HBCD) is a brominated flame retardant used primarily in expanded (EPS) and extruded (XPS) polystyrene foams for thermal insulation in the building and construction industry. Tetrabromobisphenol A (TBBPA) is used both as a reactive and an additive flame retardant in a variety of materials. HBCD and TBBPA contaminate the environment and are found in human blood samples. In previous studies, we have shown that other environmental contaminants, such as the dibutyltin (DBT) and tributyltin (TBT), decrease NK lytic function by activating mitogen-activated protein kinases (MAPKs) in the NK cells. HBCD and TBBPA also interfere with NK cell(s) lytic function. The current study evaluates whether HBCD and/or TBBPA have the capacity to activate MAPKs and MAPK kinases (MAP2Ks). The effects of concentrations of HBCD and TBBPA that inhibited lytic function on the phosphorylation state and total levels of the MAPKs (p44/42, p38, and JNK) and the phosphorylation and total levels of the MAP2Ks (MEK1/2 and MKK3/6) were examined. Results indicate that exposure of human NK cells to 10-0.5 μM HBCD or TBBPA activate MAPKs and MAP2Ks. This HBCD and TBBPA-induced activation of MAPKs may leave them unavailable for activation by virally infected or tumor target cells and thus contributes to the observed decreases in lytic function seen in NK cells exposed to HBCD and TBBPA.

NK cells and virus-related cancers

Natural killer (NK) cells become activated during viral infections and can play roles in such infections by attacking virus-infected cells or by regulating adaptive immune responses. Experimental models suggest that NK cells may also have the capacity to restrain virus-induced cancers. Here, we discuss the seven viruses linked to human cancers and the evidence of NK cell involvement in these systems.

Natural killer cell deficiency

Natural killer (NK) cells are part of the innate immune defense against infection and cancer and are especially useful in combating certain viral pathogens. The utility of NK cells in human health has been underscored by a growing number of persons who are deficient in NK cells and/or their functions. This can be in the context of a broader genetically defined congenital immunodeficiency, of which there are more than 40 presently known to impair NK cells. However, the abnormality of NK cells in certain cases represents the majority immunologic defect. In aggregate, these conditions are termed NK cell deficiency. Recent advances have added clarity to this diagnosis and identified defects in 3 genes that can cause NK cell deficiency, as well as some of the underlying biology. Appropriate consideration of these diagnoses and patients raises the potential for rational therapeutic options and further innovation.

Neonatal natural killer cell function: relevance to antiviral immune defense

Neonates are particularly susceptible to various pathogens compared to adults, which is attributed in part to their immature innate and adaptive immunity. Natural killer cells provide first-line innate immune reactions against virus-infected cells without prior sensitization. This review updates phenotypic and functional deficiencies of neonatal cells compared to their adult counterparts and their clinical implications.

Tributyltin and dibutyltin alter secretion of tumor necrosis factor alpha from human natural killer cells and a mixture of T cells and natural killer cells

Butyltins (BTs) have been in widespread use. Tributyltin (TBT) has been used as a biocide in a variety of applications and is found in human blood samples. Dibutyltin (DBT) has been used as a stabilizer in polyvinyl chloride plastics and as a de-worming agent in poultry. DBT, like TBT, is found in human blood. Human natural killer (NK) cells are the earliest defense against tumors and viral infections and secrete the cytokine tumor necrosis factor-alpha (TNF-α). TNF-α is an important regulator of adaptive and innate immune responses. TNF-α promotes inflammation and an association between malignant transformation and inflammation has been established. Previously, we have shown that TBT and DBT were able to interfere with the ability of NK cells to lyse tumor target cells. Here we show that BTs alter cytokine secretion by NK cells as well as a mixture of T and NK lymphocytes (T/NK cells). We examined 24-, 48-h and 6-day exposures to TBT (200-2.5 nM) and DBT (5-0.05 μM) on TNF-α secretion by highly enriched human NK cells and T/NK cells. The results indicate that TBT (200-2.5 nM) decreased TNF-α secretion from NK cells. In the T/NK cells, 200 nM TBT decreased secretion whereas 100-5 nM TBT increased secretion of TNF-α. NK cells or T/NK cells exposed to higher concentrations of DBT showed decreased TNF-α secretion whereas lower concentrations showed increased secretion. The effects of BTs on TNF-α secretion are seen at concentrations present in human blood.

Effects of DDT and triclosan on tumor-cell binding capacity and cell-surface protein expression of human natural killer cells

1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) and triclosan (TCS) are organochlorine (OC) compounds that contaminate the environment, are found in human blood and have been shown to decrease the tumor-cell killing (lytic) function of human natural killer (NK) cells. NK cells defend against tumor cells and virally infected cells. They bind to these targets, utilizing a variety of cell surface proteins. The present study examined concentrations of DDT and TCS that decrease lytic function for alteration of NK binding to tumor targets. Levels of either compound that caused loss of binding function were then examined for effects on expression of cell-surface proteins needed for binding. NK cells exposed to 2.5 μM DDT for 24 h (which caused a greater than 55% loss of lytic function) showed a decrease in NK binding function of about 22%, and a decrease in CD16 cell-surface protein of 20%. NK cells exposed to 5 μM TCS for 24 h showed a decrease in ability to bind tumor cells of 37% and a decrease in expression of CD56 of about 34%. This same treatment caused a decrease in lytic function of greater than 87%. These results indicated that only a portion of the loss of NK lytic function seen with exposures to these compounds could be accounted for by loss of binding function. They also showed that loss of binding function is accompanied by a loss of cell-surface proteins important in binding function.

The relationship between the frequency of the common cold and the activities of natural killer cells

We investigated the relationship between the frequency of the common cold and the conditions of the body's immune system among members of a generally healthy population. Self-reporting questionnaires on the frequency of the common cold and on fatigue and stress conditions were administered to a total of 67 healthy individuals aged 22 to 50. The activities of natural killer (NK) cells, which were determined by Eu(3+)-DTPA release assay, and of NK cell members in the peripheral blood of the subjects were phenotypically (CD3 CD16(+) CD56(+)) analyzed with three-color flow cytometry. The results showed that the frequency of the common cold was significantly correlated with NK activity and NK subset (CD3(-)CD16(+) CD56(+)) frequency (r=-0.34 and-0.47 respectively, P<0.01). After adjusting for age, the mean NK subset (CD3(-)CD16(+)CD56) significandy differed (F=3.384, P<0.05) among the four frequency groups for the common cold, and the frequencies of the common cold were significandy different among the four stress/fatigue groups (F=8.016, P<0.001) for the males, as evaluated by ANCOVA. These results indicate that conditions of high stress and fatigue may increase the chance of catching the common cold due to a decrease in activities of NK cells.

Pentachlorophenol decreases tumor-cell-binding capacity and cell-surface protein expression of human natural killer cells

Pentachlorophenol (PCP) is an organochlorine pesticide that decreases the tumor-cell killing (lytic) function of human natural killer (NK) cells. NK cells defend against tumor cells and virally infected cells. They bind to these targets, utilizing a variety of cell-surface proteins. This study examined concentrations of PCP that decrease lytic function for alteration of NK binding to tumor targets. Levels of PCP that caused loss of binding function were then examined for effects on expression of cell-surface proteins needed for binding. Exposure to 10 μM PCP for 24 h (which caused a greater than 70% loss of lytic function) decreased NK binding function (34.6%), and CD11a (21.7%) and CD56 (26.2%) cell-surface proteins. Both binding function and cell-surface proteins were decreased after longer exposures to lower concentrations of PCP. These data indicate that continuous exposures to PCP decreased binding function as well as cell-surface marker expression in NK cells and that these changes may in part explain the losses of lytic function seen with these exposures. PCP exposures have been shown to increase the incidence of blood and kidney cancers in humans. These data indicate that a possible explanation for this increased risk may be loss of NK lytic function, which is at least in part owing to the loss of the ability of the NK cell to bind to tumor cells. These data also indicate that lost binding function may be due to loss of important cell-surface proteins.

Unraveling human natural killer cell deficiency

NK cells are a component of the innate immune system identified in animals as serving an essential role in antiviral immunity. Establishing their role in human health has been challenging, with the most direct insight coming from the study of NK cell-deficient individuals. However, NK cell deficiencies are rare, and more research is needed. In this issue of the JCI, two independent groups of researchers have simultaneously identified the genetic cause of a human NK cell deficiency as mutation in the MCM4 gene, encoding minichromosome maintenance complex component 4. These reports suggest a critical role for the minichromosome maintenance helicase complex in NK cells and NK cell-mediated host defense.

Tetrabromobisphenol A decreases cell-surface proteins involved in human natural killer (NK) cell-dependent target cell lysis

Human natural killer (NK) lymphocytes are able to destroy tumor cells and virally-infected cells. Interference with their function can leave an individual with increased susceptibility to cancer development and/or viral infection. We have shown that the tumor-destroying (lytic) function of NK cells can be dramatically decreased by exposure to the environmental contaminant tetrabromobisphenol A (TBBPA). TBBPA is a flame retardant used in a variety of materials including circuit boards, carpeting, and upholstery and has been found in human blood samples. TBBPA interferes with NK cell lytic function, in part, by decreasing the ability of NK cells to bind to target cells. This study examines the effects of exposures to concentrations of TBBPA (i.e., that were able to decrease the binding capacity of NK cells) on the expression of cell-surface proteins (CD2, CD11a, CD16, CD18, and CD56) that are needed for NK cells to bind target cells. NK cells were exposed to TBBPA for 24 h, 48 h, and 6 days or for 1 h followed by 24 h, 48 h, and 6 days in TBBPA-free media. Twenty-four-hour exposures to 5 µM TBBPA caused decreases in four of the cell-surface proteins examined. CD16 was decreased by >35%. The decreases in cell-surface proteins after a 48-h exposure were similar to those seen after 24 h. The results indicate that TBBPA exposures that decrease the binding function of human NK cells do so by decreasing the expression of cell-surface proteins needed for attachment of NK cells to targets cells.

NK cells, innate immunity and hepatitis C infection after liver transplantation

Liver transplantation in patients with active hepatitis C virus (HCV) infection is followed by almost universal recurrence of viral infection. The control of HCV infection has been characterized largely in terms of the HCV-specific function of T-lymphocytes and the adaptive immune response. Emerging data suggest that components of the innate immune system, including natural killer cells, have a central role in determining the nature of posttransplant HCV infection and the likelihood of response to antiviral therapy. This review examines the emerging evidence implicating innate immunity in the pathogenesis of posttransplant HCV infections and the potential therapeutic implications of these observations.

Natural killer cell licensing during viral infection

Natural Killer (NK) cell functionality is controlled by inhibitory receptors that recognize self-MHC class I. NK cells that do not interact with self-MHC class I are hypo-responsive to many stimuli and fail to reject MHC class I-deficient cells. Thus, although the mechanisms are unknown, interactions with MHC class I "licensed" NK cells respond efficiently. Surprisingly, these licensed NK cells fail to control viral infection. During mouse cytomegalovirus (MCMV) infection, SHP-1 signaling downstream of inhibitory receptors for MHC class I limits NK cell proliferation. Interactions with MHC class I prevent licensed NK cells from controlling of MCMV replication and pathogenesis; rather, it is the unlicensed NK cells that are not inhibited by self-MHC class I that efficiently control MCMV infection. Therefore, the licensing hypothesis is not sufficient to explain NK cell functionality during viral infection.

Activation of p44/42 in human natural killer cells decreases cell-surface protein expression: Relationship to tributyltin-induced alterations of protein expression

Tributyltin (TBT) activates the mitogen activated protein kinase (MAPK), p44/42 in human natural killer (NK) cells. TBT also reduces NK cytotoxic function and decreases the expression of several NK-cell proteins. To understand the role that p44/42 activation plays in TBT-induced loss of NK cell function, this study investigated how selective activation of p44/42 by phorbol 12-myristate 13-acetate (PMA) affects NK cells. Previously it was shown that PMA caused losses of lytic function similar to those seen with TBT exposures. This study examined activation of p44/42 in the regulation of NK-cell protein expression and how this regulation may explain the protein expression changes seen with TBT exposures. NK cells exposed to PMA were examined for levels of cell-surface proteins, granzyme mRNA, and perforin mRNA expression. The expression of CD11a, CD16, CD18, and CD56 were reduced, perforin mRNA levels were unchanged, and granzyme mRNA levels were increased. To verify that activation of p44/42 was responsible for the alterations seen in CD11a, CD16, CD18, and CD56 with PMA, NK cells were treated with the p44/42 pathway inhibitor (PD98059) prior to PMA exposures. In the presence of PD98059, PMA caused no decreases in the expression of the cell-surface proteins. Results of these studies indicate that the activation of p44/42 may lead to the loss of NK cell cytotoxic function by decreasing the expression of CD11a, CD16, CD18, and CD56. Further, activation of p44/42 appears to be at least in part responsible for the TBT-induced decreases in expression of CD16, CD18, and CD56.

Role of protein kinase C in TBT-induced inhibition of lytic function and MAPK activation in human natural killer cells

Human natural killer (NK) cells are lymphocytes that destroy tumor and virally infected cells. Previous studies have shown that exposure of NK cells to tributyltin (TBT) greatly diminishes their ability to destroy tumor cells (lytic function) while activating mitogen-activated protein kinases (MAPK) (p44/42, p38, and JNK) in NK cells. The signaling pathway that regulates NK lytic function appears to include activation of protein kinase C(PKC) as well as MAPK activity. TBT-induced activation of MAPKs would trigger a portion of the NK lytic signaling pathway, which would then leave the NK cell unable to trigger this pathway in response to a subsequent encounter with a target cell. In the present study we evaluated the involvement of PKC in inhibition of NK lysis of tumor cells and activation of MAPKs caused by TBT exposure. TBT caused a 2–3-fold activation of PKC at concentrations ranging from 50 to 300 nM (16–98 ng/ml),indicating that activation of PKC occurs in response to TBT exposure. This would then leave the NK cell unable to respond to targets. Treatment with the PKC inhibitor, bisindolylmaleimide I, caused an 85% decrease in the ability of NK cells to lyse tumor cells, validating the involvement of PKC in the lytic signaling pathway. The role of PKC in the activation of MAPKs by TBT was also investigated using bisindolylmaleimide I. The results indicated that, in NK cells where PKC activation was blocked, there was no activation of the MAPK, p44/42 in response to TBT.However, TBT-induced activation of the MAPKs, p38 and JNK did not require PKC activation. These results indicate the pivotal role of PKC in the TBT-induced loss of NK lytic function including activation of p44/42 by TBT in NK cells.

Activation of p44/42 MAPK plays a role in the TBT-induced loss of human natural killer (NK) cell function

Natural killer (NK) cells destroy (lyse) tumor cells, virally infected cells, and antibody-coated cells. Previous studies indicated that exposure to the environmental contaminant tributyltin (TBT) decreases the lytic function of NK cells and activates mitogen-activated protein kinases (MAPK), including p44/42 (Aluoch and Whalen Toxicology 209:263-277, 2005). If activation of p44/42 is required for TBT-induced decreases of lytic function, then activation of p44/42 to similar extents by pharmacological agents such as phorbol 12-myristate 13-acetate (PMA) should mimic to some extent changes induced in NK cells with TBT exposures. NK cells were exposed to PMA concentrations between 0.25 and 10 nM for 10 min, 1 h, and 6 h before determining the lytic function ((51)Cr release assay) and phosphorylation state of MAPKs (Western blot). A 1-h exposure of NK cells to 5 nM PMA resulted in a loss of lytic function of 47%. Western blot analysis showed that a 1-h exposure to 5 nM PMA caused a sixfold increase in phospho-p44/42 levels. Previous studies showed a fivefold increase in phospho-p44/42 in response to a 1-h exposure to 300 nM TBT. Exposure to 300 nM TBT caused about a 40% decrease in lytic function. This study supports the hypothesis that p44/42 activation (as seen with TBT exposures) can cause a loss of NK-cell lytic function.

Immunosuppressive effects of triclosan, nonylphenol, and DDT on human natural killer cells in vitro

Human natural killer (NK) cells are a first-line immune defense against tumor cells and virally-infected cells. If their function is impaired, it leaves an individual more susceptible to cancer development or viral infection. The ability of compounds that contaminate the environment to suppress the function of NK cells could contribute to the increased risk of cancer development. There are a wide spectrum of compounds that significantly contaminate water and food that are consumed by humans, leading to accumulation of some of these compounds in human tissues. In the current study, we examined the ability of three such compounds to diminish the function of human NK cells. Triclosan (TC) is an antimicrobial agent used in a large number of antibacterial soaps. Nonylphenol (NP) is a degradation product of compounds used as surfactants and as stabilizers in plastics. 4,4'-Dichlorodiphenyltrichloroethane (DDT) is a pesticide that is mainly used to control mosquitoes. The compounds were examined for their ability to suppress NK function following exposures of 1 h, 24 h, 48 h, and 6 days. Each agent was able to substantially decrease NK lytic function within 24 h. At a concentration of 5 microM, both TC and NP inhibited NK lytic function by 87 and 30%, respectively; DDT decreased function by 55% at 2.5 microM. The negative effects of each of these compounds persisted and/or intensified following a brief (1 h) exposure to the compounds, indicating that the impairment of function cannot be eliminated by removal of the compound under in vitro conditions.

Effects of butyltin exposures on MAP kinase-dependent transcription regulators in human natural killer cells

Natural killer (NK) cells are a major immune defense mechanism against cancer development and viral infection. The butyltins (BTs), tributyltin (TBT) and dibutyltin (DBT), have been widely used in industrial and other applications and significantly contaminate the environment. Both TBT and DBT have been detected in human blood. These compounds inhibit the lytic and binding function of human NK cells and thus could increase the incidence of cancer and viral infections. Butyltin (BT)-induced loss of NK function is accompanied by activation of mitogen activated protein kinases (MAPKs) and decreases in expression of cell-surface and cytolytic proteins. MAPKs activate components of the transcription regulator AP-1 and activate the transcription regulator Elk-1. Based on the fact that BTs activate MAPKs and alter protein expression, the current study examined the effect of BT exposures on the levels and phosphorylation states of the components of AP-1 and the phosphorylation state of Elk-1. Exposure to 300 nM TBT for 10 min increased the phosphorylation of c-Jun in NK cells. One hour exposures to 300 nM and 200 nM TBT increased the phosphorylation and overall level of c-Jun. During a 300 nM treatment with TBT for 1 h the binding activity of AP-1 was significantly decreased. There were no significant alterations of AP-1 components or of Elk-1 with DBT exposures. Thus, it appears that TBT-induced alterations on phosphorylation, total levels, and binding activity of c-Jun might contribute to, but are not fully responsible for, TBT-induced alterations of NK protein expression.

Hexabromocyclododecane decreases tumor-cell-binding capacity and cell-surface protein expression of human natural killer cells

Hexabromocyclododecane (HBCD) is a flame retardant that decreases the lytic function of human natural killer (NK) cells. NK cells defend against tumor cells and virally infected cells. Thus, HBCD has the potential to increase cancer incidence and viral infections. NK cells must bind to their targets for lysis to occur. Thus, concentrations of HBCD that decrease lytic function were examined for their ability to alter NK binding to tumor targets. Levels of HBCD that caused a loss of binding function were examined for effects on expression of cell surface proteins needed for binding. NK cells exposed to HBCD for 24 h, 48 h or 6 days or to HBCD for 1 h followed by 24 h, 48 h or 6 days in HBCD-free media were examined for binding function and cell surface protein expression. The results indicated that exposure of NK cells to 10 microM HBCD for 24 h (which caused a greater than 90% loss of lytic function) caused a very significant decrease in NK cell binding function (70.9%), and in CD16 and CD56 cell-surface protein expression (57.8 and 24.6% respectively). NK cells exposed to 10 microM HBCD for 1 h followed by 24 h in HBCD-free media (which caused a 89.3% loss of lytic function) showed decreased binding function (79.2%), and CD 16 expression (48.1%). Results indicate that HBCD exposures decreased binding function as well as cell-surface marker expression in NK cells and that these changes may explain the losses of lytic function induced by certain HBCD exposures.

Tetrabromobisphenol A has immunosuppressive effects on human natural killer cells

Human natural killer (NK) cells are lymphocytes that destroy tumor cells, virally-infected cells, and antibody-coated cells. Tetrabromobisphenol A (TBBPA) is used both as a reactive and as an additive flame retardant in a variety of materials and appears to contaminate the environment. TBBPA has been found in human blood samples and if it interferes with NK cell function, this could increase the risk of tumor development and/or viral infection. The present study examines the effects of exposure to various concentrations of TBBPA for 24 hr, 48 hr, and 6 days on the lytic function, tumor-target-binding function, and ATP levels of NK cells. These same parameters were also monitored in NK cells that were exposed to TBBPA for 1 h followed by 24 hr, 48 hr, and 6 days in TBBPA-free media. A 24-h exposure of NK cells to 5 microM TBBPA caused a >95% decrease in NK lytic function, a 70% decrease in binding function, and a 34% decrease in ATP levels in NK cells. Exposure to 2.5 microM TBBPA for 24 h decreased lytic function by 76%, binding function by 20%, and had no effect on ATP levels. Exposure of NK cells to 5 microM TBBPA for 1 h followed by 24 h in TBBPA-free media caused a progressive and persistent loss of lytic function (41%) while not affecting either binding ability or ATP levels. The results indicate that TBBPA exposures decrease the lytic function of human NK cells and that an initial brief (1 hr) exposure can cause a progressive loss of function. In addition, the data also indicate that TBBPA-induced loss of NK lytic function can occur at a concentration of TBBPA that does not affect target-binding ability and ATP levels of NK cells.

Increases in cytosolic calcium ion levels in human natural killer cells in response to butyltin exposure

This study investigated whether exposures to butyltins (BTs), tributylin (TBT), and dibutyltin (DBT) were able to alter cytosolic calcium levels in human natural killer (NK) cells. Additionally, the effects of cytosolic calcium ion increases on the activation state of mitogen-activated protein kinases (MAPKs) in NK cells were also investigated. NK cells are an intital immune defense against the development of tumors or viral infections. TBT and DBT are widespread environmental contaminants, due to their various industrial applications. Both TBT and DBT have been shown to decrease the ability of NK cells to lyse tumor cells (lytic function). TBT has also been shown to activate MAPKs in NK cells. The results of this study indicated that TBT increased cytosolic calcium levels by as much as 100% after a 60-min exposure to 500 nM TBT, whereas DBT increased cytosolic calcium levels to a much smaller extent (and required higher concentrations). The results also indicated that increases in cytosolic calcium could activate MAPKs but only for a short period of time (5 min), whereas previous studies showed that activation of MAPKs by TBT last for at least 6 h. Thus, it appears that TBT-stimulated increases in cytosolic calcium might contribute to, but are not fully responsible for, TBT-induced activation of MAPKs.

Hexabromocyclododecane decreases the lytic function and ATP levels of human natural killer cells

This study investigates the effect of hexabromocyclododecane (HBCD) on the lytic function of human natural killer (NK) cells and on ATP levels in NK cells. NK cells are capable of lysing tumor cells, virally infected cells, and antibody-coated cells. HBCD is a brominated cyclic alkane used primarily as an additive flame retardant. If HBCD interferes with NK cell function, this could increase risk of tumor development and/or viral infection. NK cells were exposed to various concentrations of HBCD for 24 and 48 h and 6 days before determining lytic function and ATP levels. ATP levels and lytic function were also determined in NK cells that were exposed to HBCD for 1 h followed by 24 and 48 h, and 6 days in HBCD-free media. The results indicated that exposure of NK cells to 10 microm HBCD for 24 h causes a very significant decrease in both NK cell lytic function and ATP levels (93.5 and 90.5%, respectively). Exposure of NK cells to 10 microm HBCD for 1 h followed by 24 h in HBCD-free media showed a progressive and persistent loss of lytic function (89.3%) as well as a decrease in ATP levels (46.1%). The results indicate that HBCD exposures decreased lytic function as well as ATP levels. However, a decrease in lytic function was not necessarily accompanied by a similar decrease in ATP. Importantly, these results also indicate that a brief (1 h) exposure to HBCD causes a progressive loss of lytic function over a 6 day period.

Glutathione diminishes tributyltin- and dibutyltin-induced loss of lytic function in human natural killer cells

This study investigated whether reduced glutathione (GSH) was able to alter the negative effects of tributyltin (TBT) or dibutyltin (DBT) on the lytic function of human natural killer (NK) cells. NK cells are an initial immune defense against the development of tumors or viral infections. TBT and DBT are widespread environmental contaminants, due to their various industrial applications. Both TBT and DBT have been shown to decrease the ability of NK cells to lyse tumor cells (lytic function). The results indicated that the presence of GSH during the exposure of NK cells to TBT or DBT diminished the negative effect of the butyltin on the lytic function of NK cells. This suggests that the interaction of TBT and DBT with functionally relevant sulfhydryl groups in NK cells may be part of the mechanism by which they decrease NK lytic function.

Pentachlorophenol decreases ATP levels in human natural killer cells

Pentachlorophenol (PCP) is used as a wood preservative and is found in human blood and urine. PCP causes significant decreases in the tumor-killing (lytic) function of human natural killer (NK) cells, a critical immune defense. The current study examined the association between decreased lytic function and decreased ATP levels, as well as the ability of antioxidants (vitamin E and reduced glutathione) to prevent PCP-induced decreases in either ATP levels or lytic function. Exposure of NK cells to 10 microm PCP decreased ATP levels by 15% at 24 h, and exposure to 5 microm PCP decreased ATP levels by 32% at 48 h. No effects were seen with 0.5 microm at 48 h or with 5 microm at 24 h. However, 10 microm PCP decreased lytic function by 69% at 24 h and 5 microm decreased it by 90% at 48 h. Even 0.5 microm PCP decreased lytic function by 46% at 48 h. None of these effects were prevented by pretreatment with 1 mm vitamin E or reduced glutathione.

Serum supplementation modulates the effects of dibutyltin on human natural killer cell function

Natural killer (NK) cells are a subset of lymphocytes capable of killing tumor cells, virally infected cells and antibody-coated cells. Dibutyltin (DBT) dichloride is an organotin used as a stabilizer in polyvinylchloride (PVC) plastics and as a deworming product in poultry. DBT may leach from PVC water supply pipes and therefore poses a potential risk to human health. We previously reported diminished NK cells lysis of tumor cells following exposure to DBT in serum-free cell culture medium. However, under in vivo conditions, circulating cells will be exposed to DBT in the presence of 100% plasma; thus we investigated whether serum supplementation and incubation time modulates DBT effects on NK cell killing and the accumulation of DBT in freshly isolated NK cells, to determine whether a serum-free model accurately predicts possible effects of DBT on human NK cells under in vivo conditions. Lytic function was decreased by approximately 35% at an intracellular DBT (DBTi) concentration of 200 microM and nearly complete loss of lytic function was observed at DBTi above 300 microM for one h. However, an intracellular concentration of 50 microM DBT, achieved over 24 h of exposure in 50% serum, reduced lytic function by 50%. Thus, conditions that reflect prolonged contact with circulating DBT, in the presence of serum, suggest that NK cell activity is decreased at lower DBTi. These data indicate that the model is useful in predicting potential human effects of relatively low DBTi concentrations.

Effects of a series of triorganotins on ATP levels in human natural killer cells

Natural killer (NK) cells are our initial immune defense against viral infections and cancer development. Thus, agents that are able to interfere with their function increase the risk of cancer and/or infection. A series of triorganotins, (trimethyltin (TMT), dimethylphenyltin (DMPT), methyldiphenyltin (MDPT), and triphenyltin (TPT)) have been shown to decrease the lytic function of human NK cells. TPT and MDPT were much more effective than DMPT or TMT at reducing lytic function. This study investigates the role that decreased ATP levels may play in decreases in the lytic function of NK cells induced by these OTs. A 24 h exposure to as high as 10 muM TMT caused no decrease in ATP levels even though this level of TMT caused a greater than 75% loss of lytic function. TPT at 200 nM caused a decrease in ATP levels of about 20% while decreasing lytic function by greater than 85%. There was no association between ATP levels and lytic function for any of the compounds when NK cells were exposed for 1h or 24 h. However, after a 48 h exposure to both DMPT and TPT decreased lytic function was associated with decreased ATP levels. There was an association between decreased lytic function and decreased ATP levels after a 6 day exposure to each of the four compounds. These studies indicate that the loss of lytic function seen after 1 h and 24 h exposures to this series of organotins cannot be accounted for by decreases in ATP. However, after longer exposures loss of lytic function may be in part be attributable to inadequate ATP levels.

Effects of tributyltin on protein tyrosine kinases and phospholipase C gamma in human natural killer cells

ABSTRACT Tributyltin (TBT) has been used in wood preservation, marine antifouling paints, disinfection of circulating industrial cooling waters, and slime control in paper mills. Detectable levels have been found in human blood. Exposure to TBT decreases the tumor cell lysing (lytic) function of human natural killer (NK) lymphocytes. In this study we assessed the effects of concentrations of TBT that have been shown to decrease NK lytic function on protein tyrosine kinases (PTKs) (Syk, Zap-70, Src, and Pyk) and phospholipase C gamma (PLC-gamma) in NK cells. Exposure to 500 nM TBT caused no change in phosphorylation of any of the PTKs. A 60-min exposure of NK cells to 500 nM TBT did not significantly affect the phosphorylation state of PLC-gamma at any of the lengths of exposure. However, total levels of PLC-gamma were increased by almost 50% after this exposure. Exposure of NK cells to 300 nM TBT for 5 to 60 min caused no significant changes in the phosphorylation state PTKs or PLC-gamma. Exposure of NK cells to 200 nM TBT for 24 h caused no significant changes in the PTK phosphorylation state or total levels. Cells that were exposed to 300 nM TBT for 1 h followed by 24 h or 48 h in TBT-free media showed a significant increase in the phosphorylated forms of Syk and Zap-70 after 24 h in TBT-free media but not after 48 h. These data indicate that in vitro exposure to TBT caused no changes in PTK or PLC-gamma phosphorylation under most conditions.

Effect of dibutyltin on ATP levels in human natural killer cells

This study investigates the role that decreased ATP levels may play in dibutyltin (DBT)-induced decreases in the tumor-cell-lysing (lytic) function of natural killer (NK) cells. NK cells are a subset of lymphocytes capable of killing tumor cells, virally infected cells, and antibody coated cells. DBT is used as stabilizer in PVC plastics and has also been used as a deworming product in poultry. NK cells were exposed to various concentrations of DBT for 1 h, 24 h, 48 h, and 6 days before determining ATP levels and lytic function. ATP levels and lytic function were also determined in NK cells that were exposed to DBT for 1 h followed by 24 h, 48 h, and 6 days in DBT-free media. The results indicated that exposure of NK cells to 10 muM DBT for 1 h did not cause any significant decrease in NK cell ATP levels but did cause a very significant loss in lytic function. NK cells exposed to 500 nM DBT for 24 h showed significant loss of lytic function but showed no decrease in ATP levels. However, 48 h and 6 days exposures to those concentrations of DBT that caused decreases in tumor lysing function also caused significant decreases in ATP levels. Exposures of NK cells to varying DBT concentrations for 1 h followed by 24 h, 48 h, and 6 days in DBT free media produced effects on lytic function and ATP levels that were similar to those seen with continuous DBT exposures. The results indicate that DBT exposures decrease ATP levels in NK cells but that tumor lysing function can be reduced independent of any decreases in ATP levels. Additionally the results show that the effects of a range of DBT concentrations on ATP levels and tumor lysing function are irreversible.

Human natural killer cell deficiencies

PURPOSE OF REVIEW

Human natural killer cell deficiencies are a relevant clinical entity that provides insight into the role of natural killer cells in host defense, as well as the basic biology of natural killer cells. Since previously reviewing these disorders, significant developments warrant their reconsideration.

RECENT FINDINGS

Human natural killer cell deficiencies can occur as part of a more pervasive immunodeficiency syndrome or, rarely, in isolation. The most informative examples of the former are in the context of a known genetic defect, because the deficiency of natural killer cell development or activity can be attributed to the specific gene function. Since last reviewed, there are five human gene mutations that are now appreciated to affect natural killer cells, and additional new insights into natural killer cell biology have been obtained through seven others. Six new reports of isolated natural killer cell deficiencies, as well as a suggested classification scheme, are also reviewed.

SUMMARY

Appreciation of human genetic syndromes that include natural killer cell deficiencies, as well as new cases of isolated natural killer cell deficiencies, continue to advance the understanding of natural killer cell biology and solidify the role of natural killer cells in defense against human herpesviral infection.

Effect of tributyltin (TBT) on ATP levels in human natural killer (NK) cells: relationship to TBT-induced decreases in NK function

The purpose of this study was to investigate the role that tributyltin (TBT)-induced decreases in ATP levels may play in TBT-induced decreases in the tumor lysing (lytic) function of natural killer (NK) cells. NK cells are a subset of lymphocytes that act as an initial immune defense against tumor cells and virally infected cells. TBT is an environmental contaminant that has been detected in human blood, which has been shown to interfere with ATP synthesis. Previous studies have shown that TBT is able to decrease very significantly the lytic function of NK cells. In this study NK cells were exposed to various concentrations of TBT and to two other compounds that interfere with ATP synthesis (rotenone a complex I inhibitor and oligomycin an ATP synthase inhibitor) for various lengths of time before determining the levels of ATP and lytic function. Exposures of NK cells to 10, 25, 50 and 100 nm TBT did not significantly reduce ATP levels after 24 h. However, these same exposures caused significant decreases in cytotoxic function. Studies of brief 1 h exposures to a range of TBT, rotenone and oligomycin concentrations followed by 24 h, 48 h and 6 day periods in compound-free media prior to assaying for ATP levels or cytotoxic function showed that each of the compounds caused persistent decreases in ATP levels and lytic function of NK cells. Exposures to 0.05-5 microm rotenone or oligomycin for 1 h reduced ATP levels by 20-25% but did not have any measurable effect on the ability of NK cells to lyse tumor cells. ATP levels were also decreased by about 20-25% after 24 h or 48 h exposures to rotenone or oligomycin (0.5 microm ), and the lytic function was decreased by about 50%. The results suggest that TBT-induced decreases in ATP levels were not responsible for the loss of cytotoxic function seen at 1 h and 24 h. However, TBT-induced decreases of NK-ATP levels may be at least in part responsible for losses of NK-cytotoxic function seen after 48 h and 6 day exposures.

Effects of organochlorine pesticides on interleukin secretion from lymphocytes

Organochlorine pesticides have been used worldwide primarily as insecticides. Due to their chemical stability, they often persist in the environment long after their use has ceased. In a previous study, we found that six organochlorine compounds (alpha-chlordane, gamma-chlordane, 4,4'-DDT, heptachlor, oxychlordane, and pentachlorophenol (PCP)), at concentrations of 5 microM, were able to significantly decrease the ability of highly purified human natural killer (NK) cells to lyse tumor cells after exposures, ranging from 1 hour to 6 days. However, if T cells were present with the NK cells (T/NK cells), loss of lytic function was seen only with oxychlordane and PCP. The purpose of the current study is to begin to investigate the mechanism by which T cells may be blocking the negative effects of some organochlorine compounds on NK cell function. Here, we investigated the hypothesis that T cells could produce significant levels of NK-stimulatory interleukin(s) (ILs), and that this may account for the decreased inhibition seen with organochlorine exposures when T cells were present. Secretion of four cytokines that have a demonstrated capacity to influence NK function, and/or are secreted by T cells, was measured (IL-2, IL-4, IL-10, IL-12). We measured both the baseline levels of ILs and the effects of organochlorine compound on IL secretion in T/NK cells. The results showed that baseline levels of the NK-stimulatory IL, IL-12, were 898 +/- 264 pg/mL at 24 hours and IL-10 levels were 564 +/- 337 pg/mL. In contrast, IL-2 levels were 14 +/- 10 pg/mL, and IL-4 levels were 3 +/- 2 pg/mL at 24 hours. The two compounds that retained their capacity to decrease NK lytic function in T/NK cells, oxychlordane (5 microM) and PCP (5 and 10 microM), were able to either decrease the secretion of NK-stimulatory ILs (IL-2, IL-12 and/or IL-10) and/or increase secretion of the NK-inhibitory cytokine, IL-4, at each length of exposure tested.

Effect of a series of triorganotins on the immune function of human natural killer cells

Natural killer (NK) cells are our initial immune defense against viral infections and cancer development. They are able to destroy tumor and virally infected cells. Thus, agents that are able to interfere with their function increase the risk of cancer and/or infection. Organotins (OTs) have been shown to interfere with the tumor-destroying function of human NK cells. The purpose of the current study was to explore the relationship of a series of triorganotins, that differ in structure by only a single organic group, for their capacity to block NK tumor-cell destroying (lytic) function. Here we examine the series: trimethyltin (TMT), dimethylphenyltin (DMPT), methyldiphenyltin (MDPT), and triphenyltin (TPT). NK cells were exposed to TMT, DMPT, MDPT or TPT for 1, 24, 48h, or 6d. A 1h exposure to TMT, at concentrations as high as 20μM, had no effect on lytic function. However, concentrations as low as 2.5μM were able to decrease NK tumor-destroying function after 6d. A 1h exposure to DMPT had no effect on lytic function, however, after 6d there was an 80-90% decrease in lytic function at 1μM. Exposure to MDPT (as low as 2.5μM) decreased NK function at 1h, after 6d there was as much as a 90% decrease at concentrations as low as 100nM MDPT. TPT decreased lytic function in a manner similar to MDPT, however, it was more effective at 1h than MDPT. The effect of the triorganotins on the ability of NK cells to bind to targets was studied, to determine if this contributed to the loss of lytic function. The relative immunotoxic potential of this series of compounds is TPT≈MDPT>DMPT>TMT.

Natural killer-dendritic cell cross-talk in cancer immunotherapy

Natural killer (NK) cells and dendritic cells (DCs), two important components of the immune system, can exchange bidirectional activating signals in a positive feedback. Myeloid DCs, the cell type specialised in the presentation of antigen and initiation of antigen-specific immune responses, have recently been documented to be involved in supporting innate immunity, promoting the production of cytokines and cytotoxicity of NK cells, and enhancing their tumouricidal activity. Natural interferon-producing cells/plasmacytoid DCs (IPCs/PDCs) play an additional role in NK cell activation. Reciprocally, NK cells, traditionally considered to be major innate effector cells, have also recently been shown to play immunoregulatory 'helper' functions, being able to activate DCs and to enhance their ability to produce pro-inflammatory cytokines, and to stimulate T helper (Th) 1 and cytotoxic T lymphocyte (CTL) responses of tumour-specific CD4+ and CD8+ T cells. Activated NK cells induce the maturation of myeloid DCs into stable type-1 polarised DCs (DC1), characterised by up to a 100-fold enhanced ability to produce IL-12p70 in response to subsequent interaction with Th cells. In addition, the ability of NK cells to kill tumour cells may facilitate the generation of tumour-related antigenic material, further accelerating the induction of tumour-specific immunity. DC1, induced by NK cells or by NK cell-related soluble factors, are stable, resistant to tumour-related suppressive factors, and demonstrate a strongly enhanced ability to induce Th1 and CTL responses in human in vitro and mouse in vivo models. Compared with the standard mature DCs that are used in clinical trials at present, human NK cell-induced DC1s act as superior inducers of anticancer CTL responses during in vitro sensitisation. This provides a strong rationale for the combined use of NK cells and DCs in the immunotherapy of patients with cancer and patients with chronic infections that are resistant to standard forms of treatment. Stage I/II clinical trials that are being implemented at present should allow evaluation of the immunological and clinical efficacy of combined NK-DC therapy of melanoma and other cancers.

Dibutyltin exposure decreases granzyme B and perforin in human natural killer cells

Natural killer (NK) cells are a subset of lymphocytes that are capable of killing tumor and virally-infected cells. Dibutyltin (DBT) is a catalyst in the production of PVC plastics and a breakdown product of tributyltin (TBT). DBT is a significant environmental contaminant. This study investigates the mechanism by which DBT exposure decreases the immune function of human NK cells. NK cells destroy their target cells by releasing cytotoxic proteins, perforin, and granzyme B. We examined the effect of DBT exposures on the levels of cytotoxic proteins and their mRNAs. Exposure of NK cells to DBT for 1h caused significant decreases in the mRNAs for granzyme B and perforin but not in protein levels. A 24h exposure to DBT decreased mRNAs as well as protein levels for both granzyme B and perforin. Exposure to DBT for 1h followed by either a 24 or 48h period in DBT-free media, decreased levels of granzyme B and perforin. The results indicate that decreases in granzyme B and perforin levels in NK cells are consequences of DBT exposure. Additionally, DBT causes rapid decreases in mRNAs for perforin and granzyme B, suggesting decreases in transcription and/or increases in mRNA degradation.

Effects of interleukins 2 and 12 on TBT-induced alterations of MAP kinases p38 and p44/42 in human natural killer cells

NK cells are lymphocytes in the non-adaptive immune system that protect the body against intracellular pathogens and eliminate tumor cells. Tributyltin (TBT) is a toxic chemical that has been detected in human foods as well as in human blood. The role of TBT in immunosuppression has been described, including inhibition of the human NK-cell cytotoxic function. Previous studies indicated that exposure of NK cells to TBT for 1 h induced progressive and irreversible inhibition of cytotoxic function. However, it was found that if NK cells were incubated in TBT-free media with either IL-2 or IL-12, loss of cytotoxic function was prevented/reversed within 24 h. Molecular studies established that loss of cytotoxic function is accompanied by alteration of MAP kinases (MAPKs) p38 and p44/42 phosphorylation. This study examined whether interleukin-mediated recovery of cytotoxicity involved reversal of tributyltin-altered p38 and p44/42 phosphorylation. The results indicated that there was no substantial IL-2 prevention/reversal of the TBT-induced alteration of phosphorylation of either p38 or p44/42 after either a 24 or 48 h recovery period. Additionally, IL-12 caused no substantial prevention/reversal of the TBT-induced alteration of phosphorylation of the MAPKs seen after either 24 or 48 h. These data suggest that IL-2 and/or IL-12-mediated recovery of NK cytotoxic function is not a result of prevention/reversal of TBT-induced phosphorylation of p38 and p44/42 MAPKs at the 24 or 48 h time points.

Review of hemophagocytic lymphohistiocytosis (HLH) in children with focus on Japanese experiences

Hemophagocytic lymphohistiocytosis (HLH) is characterized by fever and hepatosplenomegaly associated with pancytopenia, hypertriglyceridemia and hypofibrinogenemia. Increased levels of cytokines and impaired natural killer activity are biological markers of HLH. HLH can be classified into two distinct forms, including primary HLH, also referred to as familial hemophagocytic lymphohistiocytosis (FHL), and secondary HLH. Although FHL is an autosomal recessive disorder typically occurring in infancy, it is important to clarify that the disease may also occur in older patients. It is now considered that FHL is a disorder of T-cell function; moreover, clonal proliferation of T lymphocytes is observed in a few FHL patients, and cytotoxicity of these T lymphocytes for target cells is usually impaired. In 1999, perforin gene (PRF1) mutation was identified as a cause of 20-30% of FHL (FHL2) cases. In Japan, two specific mutations of PRF1 were also detected. Furthermore, in 2003, MUNC13-4 mutations were identified in some non-FHL2 patients (FHL3). Identification of other genes responsible for remaining cases is a major concern. Hematopoietic stem cell transplantation (HSCT) has been established as the only accepted curative therapy for FHL. Thus, appropriate diagnosis and prompt treatment with HSCT are necessary for FHL patients. Genetic analysis for PRF1 and MUNC13-4 and functional assay of cytotoxic T lymphocytes are recommended to be performed in each patient. In those patients displaying impaired cytotoxic function but lacking genetic defects, samples should be employed for identification of unknown genes. In the near future, an entire pathogenesis should be clarified in order to establish appropriate therapies including immunotherapy, HSCT and gene therapy.

Persistent inhibition of human natural killer cell function by ziram and pentachlorophenol

Ziram is a currently used agricultural fungicide. It is also used as an additive in the production of latex gloves. Because of these uses, there is a potential for human exposure to this compound. Pentachlorophenol (PCP) has been used as an insecticide, fungicide, disinfectant, and ingredient in antifouling paints. Currently, it is used as a wood preservative for power-line poles and fence posts. Measurable levels of PCP have been detected in human blood and urine. In previous studies we demonstrated that both these compounds could cause very significant inhibition of the tumor-killing function of human natural killer (NK) cells. NK lymphocytes play a central role in immune defense against viral infection and the formation of primary tumors. So interference with their function could increase the risk of tumor development. In the present study we examined the effects of exposure to ziram or PCP of brief duration (1 h) on the ability of NK cells to destroy tumor cells. NK cells were exposed to either ziram (5-0.5 microM) or PCP (10-5 microM) for 1 h followed by 0 h, 24 h, 48 h, or 6 days in compound-free media and then were tested for the ability to lyse as well as to bind tumor cells. A 1-h exposure to as little as 2.5 microM ziram decreased the ability of NK cells to lyse target tumor cells, which persisted up to 6 days following exposure. The loss of lytic function for from 24 h to 6 days following exposure was accompanied by a comparable loss of NK capacity to bind tumor cells. Exposure to 10 microM PCP for 1 h caused a progressive loss (greater than 80%) of lytic function within 6 days of exposure. In contrast to ziram, PCP exposure caused no accompanying loss of binding function.

Effects of interleukins 2 and 12 on the levels of granzyme B and perforin and their mRNAs in tributyltin-exposed human natural killer cells

Natural killer (NK) cells are a subset of lymphocytes that are capable of killing tumor cells, virally infected cells and antibody coated cells. Tributyltin (TBT) is a toxic chemical used for various industrial purposes such as: slime control in paper mills, disinfection of circulating industrial cooling waters, anti-fouling agents, and the preservation of wood. TBT can be found in edible items such as fish. A previous study showed that a 1 h exposure of NK cells to TBT caused persistent inhibition of NK-cell ability to destroy tumor cells in the 24 and 48 h periods following exposure and that this loss of function could be significantly prevented and/or reversed if the NK-stimulatory interleukins (IL) 2 or 12 were present during the 24 and 48 h periods. We had also shown that TBT exposure was able to significantly decrease the protein and mRNA levels of the cytotoxic proteins, granzyme B and perforin, and the phosphorylation of cAMP-response-element-binding protein (CREB) under these conditions. In this study we address the effects of IL-2 and IL-12 on the TBT-induced decreases in NK-cell levels of the cytotoxic proteins, their mRNAs, and CREB phosphorylation. IL-2 appeared to prevent/reverse TBT-induced declines in perforin protein levels and the mRNA for perforin seen in the 24 h period following a 1 h exposure to 300 nM TBT. However, the TBT-induced decreases in the levels of perforin and perforin mRNA seen in the 48 h period following a 1 h exposure to TBT were not statistically significantly prevented/reversed by IL-2. Additionally, the TBT-induced decreases in granzyme B, granzyme B mRNA, and CREB phosphorylation were not statistically significantly reversed by either IL-2 or IL-12 after 24 or 48 h.

Tributyltin-induced effects on MAP kinases p38 and p44/42 in human natural killer cells

NK cells form a class of lymphocytes that are able to kill tumor cells, virally infected cells and antibody-coated cells without prior sensitization. Tributyltin (TBT) is a toxic chemical that was used in large scale in wood preservation, marine antifouling paints, and slime control in paper mills. TBT has been detected in human foods such as dairy products, meat and fish and detectable levels have been found in human blood. The role of TBT in immunosuppression has been reported and its specific inhibition of the human NK-cell cytotoxic function has also been described. The current studies examined the role of mitogen-activated protein kinases (MAPKs) p38 and p44/42 during TBT-induced inhibition of NK cytotoxic function. Continuous in vitro exposure to 300 nM TBT for 1h decreased the NK cell cytotoxic function with concomitant increases in phosphorylated forms of both p38 and p44/42 but not the total levels of either of these enzymes. Similar results were obtained with 500 nM TBT treatment. A 1 h exposure to 300 nM TBT followed by 24 h in TBT-free media resulted in a further decrease in the cytotoxic function with an accompanying increase in the phosphorylated forms of p38 and p44/42 MAPKs as compared to controls (approximately 50%). However, after 48 h in TBT-free media, the phosphorylation levels of both p44/42 and p38 MAPKs decreased by about 50 and 30%, respectively. NK cell cytotoxic function also continued to decrease with time in TBT-free media. A 24h exposure to 200 nM TBT decreased cytotoxic function of NK cells (>90%) but produced donor-dependent effects on the phosphorylated p38 and p44/42 MAPK levels. These data indicated that in vitro exposures to TBT induced changes in the phosphorylation (activation) states of p38 and p44/42 but not in their overall levels of expression in human NK cells.