Characterization of functional surface structures on human natural killer cells

Circulating multimeric immune complexes contribute to immunopathology in COVID-19

A dysregulated immune response with high levels of SARS-CoV-2 specific IgG antibodies characterizes patients with severe or critical COVID-19. Although a robust IgG response is considered to be protective, excessive triggering of activating Fc-gamma-receptors (FcγRs) could be detrimental and cause immunopathology. Here, we document excessive FcγRIIIA/CD16A activation in patients developing severe or critical COVID-19 but not in those with mild disease. We identify two independent ligands mediating extreme FcγRIIIA/CD16A activation. Soluble circulating IgG immune complexes (sICs) are detected in about 80% of patients with severe and critical COVID-19 at levels comparable to active systemic lupus erythematosus (SLE) disease. FcγRIIIA/CD16A activation is further enhanced by afucosylation of SARS-CoV-2 specific IgG. Utilizing cell-based reporter systems we provide evidence that sICs can be formed prior to a specific humoral response against SARS-CoV-2. Our data suggest a cycle of immunopathology driven by an early formation of sICs in predisposed patients. These findings suggest a reason for the seemingly paradoxical findings of high antiviral IgG responses and systemic immune dysregulation in severe COVID-19. The involvement of circulating sICs in the promotion of immunopathology in predisposed patients opens new possibilities for intervention strategies to mitigate critical COVID-19 progression.

During viral infections high levels of antibodies can form soluble immune complexes (sICs) with antigen and trigger Fcγ receptors (FcγR) leading to increased immunopathology. Here the authors measure FcγRs activation by sICs and consider how these may lead to excessive immunopathology during severe SARS-CoV-2 infection.

The War Is on: The Immune System against Glioblastoma—How Can NK Cells Drive This Battle?

Natural killer (NK) cells are innate lymphocytes that play an important role in immunosurveillance, acting alongside other immune cells in the response against various types of malignant tumors and the prevention of metastasis. Since their discovery in the 1970s, they have been thoroughly studied for their capacity to kill neoplastic cells without the need for previous sensitization, executing rapid and robust cytotoxic activity, but also helper functions. In agreement with this, NK cells are being exploited in many ways to treat cancer. The broad arsenal of NK-based therapies includes adoptive transfer of in vitro expanded and activated cells, genetically engineered cells to contain chimeric antigen receptors (CAR-NKs), in vivo stimulation of NK cells (by cytokine therapy, checkpoint blockade therapies, etc.), and tumor-specific antibody-guided NK cells, among others. In this article, we review pivotal aspects of NK cells’ biology and their contribution to immune responses against tumors, as well as providing a wide perspective on the many antineoplastic strategies using NK cells. Finally, we also discuss those approaches that have the potential to control glioblastoma—a disease that, currently, causes inevitable death, usually in a short time after diagnosis.

Cytokines and signaling pathways involved in differentiation potential of hematopoietic stem cells towards natural killer cells

NK cells are innate immune cells derived from common lymphoid progenitor and are developed primarily in the bone marrow. These cells respond to stress signals, inflammatory cytokines, and cancerous cells through the secretion of active immune mediators. Previous studies revealed that NK cells can be used as an essential cell in the defense against cancers. According to the literature, a set of cytokines and factors play a crucial role during differentiation of NK cells. In other words, developmental events of NK cells are regulated through multiple critical cytokines, including interleukins (ILs), kit ligand, fms-like tyrosine kinase three ligand, transforming growth factor-β, and typical γ chain family of cytokines. Among previously investigated ILs, IL-2, IL-3, IL-7, and IL-15 are the most important. In addition to ILs, transcription factors and MicroRNAs are involved in NK cell development. In this review study, after presenting a brief description of developmental stages and production of the NK cells, the factors and signaling pathways involved in differentiation of NK cells were discussed.

The role of NK cells in fighting the virus infection and sepsis

Natural killer cells, one of the important types of innate immune cells, play a pivotal role in the antiviral process in vivo. It has been shown that increasing NK cell activity may promote the alleviation of viral infections, even severe infection-induced sepsis. Given the current state of the novel coronavirus (SARS-CoV-2) global pandemic, clarifying the anti-viral function of NK cells would be helpful for revealing the mechanism of host immune responses and decipher the progression of COVID-19 and providing important clues for combating this pandemic. In this review, we summarize the roles of NK cells in viral infection and sepsis as well as the potential possibilities of NK cell-based immunotherapy for treating COVID-19.

IL-18 Responsiveness Defines Limitations in Immune Help for Specialized FcRγ- NK Cells

Despite being prolific innate killers, NK cells are also key helper cells in antiviral defense, influencing adaptive immune responses via interactions with dendritic cells (DCs). In addition to causing NK cell dysfunction, HIV-1 infection contributes to the expansion of a rare population of NK cells deficient in FcRγ (FcRγ^-), an intracellular adaptor protein that associates with CD16. The implications of this inflated NK cell subset in treated HIV-1 infection remain unclear. In this study, we explored the helper function of human NK cells in chronic HIV-1 infection, with a particular focus on characterizing FcRγ^- NK cells. Exposure of NK cells to innate DC-derived costimulatory factors triggered their helper activity, defined by their ability to produce IFN-γ and to drive the maturation of high IL-12-producing DCs. In this setting, however, FcRγ^- NK cells were defective at producing the dominant DC-polarizing agent IFN-γ. The reduced responsiveness of FcRγ^- NK cells to IL-18 in particular, which was attributable to impaired inducible expression of IL-18Rα, extended beyond an inability to produce IFN-γ, as FcRγ^- NK cells showed limited potential to differentiate into CD16^-/CD25⁺/CD83⁺ helper cells. Notwithstanding their deficiencies in responsiveness to innate environmental cues, FcRγ^- NK cells responded robustly to adaptive Ab-mediated signaling through CD16. The presence of an expanded population of FcRγ^- NK cells with a diminished capacity to respond to IL-18 and to effectively modulate DC function may contribute to disturbances in proper immune homeostasis associated with HIV-1 infection and to defects in the initiation of optimal adaptive antiviral responses.

NK Cell Adoptive Immunotherapy of Cancer: Evaluating Recognition Strategies and Overcoming Limitations

Natural killer (NK) cells, the primary effector cells of the innate immune system, utilize multiple strategies to recognize tumor cells by (1) detecting the presence of activating receptor ligands, which are often upregulated in cancer; (2) targeting cells that have a loss of major histocompatibility complex (MHC); and (3) binding to antibodies that bind to tumor-specific antigens on the tumor cell surface. All these strategies have been successfully harnessed in adoptive NK cell immunotherapies targeting cancer. In this review, we review the applications of NK cell therapies across different tumor types. Similar to other forms of immunotherapy, tumor-induced immune escape and immune suppression can limit NK cell therapies' efficacy. Therefore, we also discuss how these limitations can be overcome by conferring NK cells with the ability to redirect their tumor-targeting capabilities and survive the immune-suppressive tumor microenvironment. Finally, we also discuss how future iterations can benefit from combination therapies with other immunotherapeutic agents.

Selective induction of antibody effector functional responses using MF59-adjuvanted vaccination

Seasonal and pandemic influenza infection remains a major public health concern worldwide. Driving robust humoral immunity has been a challenge given preexisting, often cross-reactive, immunity and in particular, poorly immunogenic avian antigens. To overcome immune barriers, the adjuvant MF59 has been used in seasonal influenza vaccines to increase antibody titers and improve neutralizing activity, translating to a moderate increase in protection in vulnerable populations. However, its effects on stimulating antibody effector functions, including NK cell activation, monocyte phagocytosis, and complement activity, all of which have been implicated in protection against influenza, have yet to be defined. Using systems serology, we assessed changes in antibody functional profiles in individuals who received H5N1 avian influenza vaccine administered with MF59, with alum, or delivered unadjuvanted. MF59 elicited antibody responses that stimulated robust neutrophil phagocytosis and complement activity. Conversely, vaccination with MF59 recruited NK cells poorly and drove moderate monocyte phagocytic activity, both likely compromised because of the induction of antibodies that did not bind FCGR3A. Collectively, defining the humoral antibody functions induced by distinct adjuvants may provide a path to designing next-generation vaccines that can selectively leverage the humoral immune functions, beyond binding and neutralization, resulting in better protection from infection.

Extra-Neutralizing FcR-Mediated Antibody Functions for a Universal Influenza Vaccine

While neutralizing antibody titers measured by hemagglutination inhibition have been proposed as a correlate of protection following influenza vaccination, neutralization alone is a modest predictor of protection against seasonal influenza. Instead, emerging data point to a critical role for additional extra-neutralizing functions of antibodies in protection from infection. Specifically, beyond binding and neutralization, antibodies mediate a variety of additional immune functions via their ability to recruit and deploy innate immune effector function. Along these lines, antibody-dependent cellular cytotoxicity, antibody-mediated macrophage phagocytosis and activation, antibody-driven neutrophil activation, antibody-dependent complement deposition, and non-classical Fc-receptor antibody trafficking have all been implicated in protection from influenza infection. However, the precise mechanism(s) by which the immune system actively tunes antibody functionality to drive protective immunity has been poorly characterized. Here we review the data related to Fc-effector functional protection from influenza and discuss prospects to leverage this humoral immune activity for the development of a universal influenza vaccine.

Influenza Virus Infection Enhances Antibody-Mediated NK Cell Functions via Type I Interferon-Dependent Pathways

Natural killer (NK) cells are an important component in the control of influenza virus infection, acting to both clear virus-infected cells and release antiviral cytokines. Engagement of CD16 on NK cells by antibody-coated influenza virus-infected cells results in antibody-dependent cellular cytotoxicity (ADCC). Increasing the potency of antibody-mediated NK cell activity could ultimately lead to improved control of influenza virus infection. To understand if NK cells can be functionally enhanced following exposure to influenza virus-infected cells, we cocultured human peripheral blood mononuclear cells (PBMCs) with influenza virus-infected human alveolar epithelial (A549) cells and evaluated the capacity of NK cells to mediate antibody-dependent functions. Preincubation of PBMCs with influenza virus-infected cells markedly enhanced the ability of NK cells to respond to immune complexes containing hemagglutinin (HA) and anti-HA antibodies or transformed allogeneic cells in the presence or absence of a therapeutic monoclonal antibody. Cytokine multiplex, RNA sequencing, supernatant transfer, Transwell, and cytokine-blocking/cytokine supplementation experiments showed that type I interferons released from PBMCs were primarily responsible for the influenza virus-induced enhancement of antibody-mediated NK cell functions. Importantly, the influenza virus-mediated increase in antibody-dependent NK cell functionality was mimicked by the type I interferon agonist poly(I·C). We conclude that the type I interferon secretion induced by influenza virus infection enhances the capacity of NK cells to mediate ADCC and that this pathway could be manipulated to alter the potency of anti-influenza virus therapies and vaccines.IMPORTANCE Protection from severe influenza may be assisted by antibodies that engage NK cells to kill infected cells through ADCC. Studies have primarily focused on antibodies that have ADCC activity, rather than the capacity of NK cells to become activated and mediate ADCC during an influenza virus infection. We found that type I interferon released in response to influenza virus infection primes NK cells to become highly reactive to anti-influenza virus ADCC antibodies. Enhancing the capacity of NK cells to mediate ADCC could assist in controlling influenza virus infections.

The Antitumor Immunity Mediated by NK Cells: The Role of The NCRs

Natural Killer (NK) cells are innate immune lymphocytes that are important for early and effective immune responses against infections and cancer. The antitumor immunity mediated by NK cells can be exerted through several direct or indirect “immunosurveillance” mechanisms that control tumor growth and prevent the rapid dissemination of metastatic tumors. NK cells express an array of activating and inhibitory receptors that enable them to recognize and bind non-self as well as self-ligands expressed on the surface of malignant or virally infected cells. The family of Natural Cytotoxicity Receptors (NCRs) comprises three activating receptors; NKp30, NKp44, and NKp46 that are important for the stimulation of NK cell effector functions. This review summarizes the mechanisms of antitumor immunity mediated by natural killer cells with focus on the role of the family of the NCRs and their tumor associated ligands.

Inhibition of histone H3K27 demethylases selectively modulates inflammatory phenotypes of natural killer cells

Natural killer (NK) cells are innate lymphocytes, important in immune surveillance and elimination of stressed, transformed, or virus-infected cells. They critically shape the inflammatory cytokine environment to orchestrate interactions of cells of the innate and adaptive immune systems. Some studies have reported that NK cell activation and cytokine secretion are controlled epigenetically but have yielded only limited insight into the mechanisms. Using chemical screening with small-molecule inhibitors of chromatin methylation and acetylation, further validated by knockdown approaches, we here identified Jumonji-type histone H3K27 demethylases as key regulators of cytokine production in human NK cell subsets. The prototypic JMJD3/UTX (Jumonji domain–containing protein 3) H3K27 demethylase inhibitor GSK-J4 increased global levels of the repressive H3K27me3 mark around transcription start sites of effector cytokine genes. Moreover, GSK-J4 reduced IFN-γ, TNFα, granulocyte–macrophage colony-stimulating factor (GM-CSF), and interleukin-10 levels in cytokine-stimulated NK cells while sparing their cytotoxic killing activity against cancer cells. The anti-inflammatory effect of GSK-J4 in NK cell subsets, isolated from peripheral blood or tissue from individuals with rheumatoid arthritis (RA), coupled with an inhibitory effect on formation of bone-resorbing osteoclasts, suggested that histone demethylase inhibition has broad utility for modulating immune and inflammatory responses. Overall, our results indicate that H3K27me3 is a dynamic and important epigenetic modification during NK cell activation and that JMJD3/UTX-driven H3K27 demethylation is critical for NK cell function.

Decrease in the Frequency of Circulating CD56+CD161+ NK Cells in Human Visceral Leishmaniasis

BACKGROUND

Natural Killer (NK) cell plays an important role in the innate immune system and is known to produce IFN-γ at an early stage of infection that is essential to eliminate intracellular infection like Leishmania spp. It is already established that Leishmania parasite inhibits the activity of NK cells, avoiding the encounter with the early innate immune response. This, in turn, favors establishment and further dissemination of the infection.

METHODS

In the present study, we have tried to measure the frequency of different phenotypic subsets of NK cells among visceral leishmaniasis (VL) patients.

RESULTS

We have phenotyped three distinct three distinct subsets (CD56^-CD161⁺, CD56⁺CD161^-, and CD56⁺CD161⁺) of NK (CD3^-) cell using their specific markers CD161 and CD56.

CONCLUSION

Interestingly, we observed selective loss of CD56⁺CD161⁺ subset of circulating NK (CD3^-) cells. Importantly, the other subsets (i.e., CD56^-CD161⁺ and CD56⁺CD161^-) of circulating NK cells remain unaffected as compared with healthy subjects.

CD56 Is a Pathogen Recognition Receptor on Human Natural Killer Cells

Aspergillus (A.) fumigatus is an opportunistic fungal mold inducing invasive aspergillosis (IA) in immunocompromised patients. Although antifungal activity of human natural killer (NK) cells was shown in previous studies, the underlying cellular mechanisms and pathogen recognition receptors (PRRs) are still unknown. Using flow cytometry we were able to show that the fluorescence positivity of the surface receptor CD56 significantly decreased upon fungal contact. To visualize the interaction site of NK cells and A. fumigatus we used SEM, CLSM and dSTORM techniques, which clearly demonstrated that NK cells directly interact with A. fumigatus via CD56 and that CD56 is re-organized and accumulated at this interaction site time-dependently. The inhibition of the cytoskeleton showed that the receptor re-organization was an active process dependent on actin re-arrangements. Furthermore, we could show that CD56 plays a role in the fungus mediated NK cell activation, since blocking of CD56 surface receptor reduced fungal mediated NK cell activation and reduced cytokine secretion. These results confirmed the direct interaction of NK cells and A. fumigatus, leading to the conclusion that CD56 is a pathogen recognition receptor. These findings give new insights into the functional role of CD56 in the pathogen recognition during the innate immune response.

Correlation Between Natural Killer Cell Activity and Systemic Inflammatory Markers for Heterogeneous Cancer Patients Treated With Wheel Balance Cancer Therapy

Background and Objective: Natural killer (NK) cells are known to have an effect on the prevention of tumorigenesis for the initial cancer, as well as the metastatic cancer. For the past several years, the relationship between cancer and inflammation has been actively studied in preclinical and clinical settings, but there are no reports on alterations in and correlation for NK cell activity (NKA) and systemic inflammatory markers. Accordingly, this study aimed to measure correlation between NKA and the levels of other systemic inflammatory markers in patients with gastric, breast, and pancreatic cancer who received Wheel Balance Cancer Therapy (WBCT). Methods: Forty-two electronic charts of patients with gastric, breast, and pancreatic cancer treated with WBCT from February 1, 2015 to September 30, 2015, were reviewed retrospectively. These charts were statistically analyzed, looking for alterations of and correlation for NKA and the expressions of systemic inflammatory markers. Results: Patients with a NKA of under 300 pg/mL at admission showed significantly higher erythrocyte sedimentation rate (ESR) and neutrophil-to-lymphocyte ratio (NLR) values and decreasing NLR values due to WBCT than patients with an NKA greater than 300 pg/mL. As a result of the correlation analysis between NKA and the levels of the systemic inflammatory markers, NKA showed significant negative correlation with NLR, ESR, and fibrinogen values. Conclusions: Negative correlation was identified between NKA and NLR, NKA and ESR, and NKA and fibrinogen in patients with heterogeneous cancer patients.

Antibody-dependent cellular cytotoxicity and influenza virus

Antibodies are a key defence against influenza infection and disease, but neutralizing antibodies are often strain-specific and of limited utility against divergent or pandemic viruses. There is now considerable evidence that influenza-specific antibodies with Fc-mediated effector functions, such as antibody-dependent cellular cytotoxicity (ADCC), can assist in the clearance of influenza infection in vitro and in animal models. Further, ADCC-mediating antibodies that recognize a broad array of influenza strains are common in humans, likely as a result of being regularly exposed to influenza infections. The concept that influenza-specific ADCC can assist in the partial control of influenza infections in humans is gaining momentum. This review examines the utility of influenza-specific ADCC antibodies.

Flow Cytometric Evaluation of Surface CD56 Expression on Activated Natural Killer Cells as Functional Marker

Surface CD56 is the most important cell marker for defining NK cells. However, the relationship between the expression of surface CD56 and NK cell activity has not yet been elucidated in detail. Thirteen healthy volunteers were enrolled in the present study. Peripheral blood mononuclear cells (PBMCs) were stimulated with rIL-2 or rIL-12 (1, 10, 100 U/mL) for 18 h at 37°C. After incubation, surface CD56 expression on NK cells was evaluated using a flow cytometric analysis. A colorimetric-based lactate dehydrogenase (LDH) assay was used for experiments on cytotoxicity. IFN-γ mRNA gene expression was quantified by real-time PCR. The expression level of surface CD56 on NK cells, cytotoxicity, and IFN-γ mRNA gene expression were significantly increased by the rIL-2 and rIL-12 stimulations. In addition, a positive correlation was found between surface CD56 expression and cytotoxic activity or IFN-γ mRNA gene expression. We revealed that the quantification of surface CD56 expression was applicable to the evaluation of cytotoxicity and IFN-γ production in activated NK cells. These results suggest that the measurement of surface CD56 expression represent an easy and rapidly reproducible technique to evaluate the activated state of NK cells and monitor NK cell activity in immunotherapy. J. Med. Invest. 63: 199-203, August, 2016.

Natural killer cells and killer-cell immunoglobulin-like receptor polymorphisms: their role in hematopoietic stem cell transplantation

Natural killer (NK) cells are important effector cells in the early control of infected, malignant, and "nonself" cells. Various receptor families are involved in enabling NK cells to detect and efficiently eliminate these target cells. The killer-cell immunoglobulin-like receptor (KIR) family is a set of receptors that are very polymorphic with regard to gene content, expression level, and expression pattern. KIRs are responsible for the induction of a NK cell alloreactive response through their interaction with HLA class I molecules. The role of NK cells in hematopoietic stem cell transplantation (HSCT) has been studied for many years, and induction of antileukemic responses by donor NK cells has been reported. Conflicting data still exist on the exact circumstances in which the KIR repertoire affects and influences clinical outcome after HSCT. More large-scale studies are needed on well-defined cohorts to unravel the mechanism of action of the NK cell-mediated alloresponse in an HSCT setting.

The dysfunction of NK cells in patients with type 2 diabetes and colon cancer

Glucose metabolism disorders influence anticarcinogenic function of natural killer (NK) cells. The aim of this study was to evaluate the number and cytotoxic activity of NK cells in type 2 diabetic (T2D) patients with negative family history of cancer, type 2 diabetic subjects with newly diagnosed untreated colon cancer (T2DCC) and patients without type 2 diabetes with newly diagnosed, untreated colon cancer (CC). Incubation tests were performed in 18 T2D patients, treated with diet and oral antidiabetic agents, 16 T2DCC; cT1-4N0M0 (c-clinical diagnosis based on computed tomography, colonoscopy and histopathology) treated with diet and oral antidiabetic agents and 16 normoglycemic CC; cT1-4N0M0. Control group included 18 metabolically healthy (with normal fasting glucose and normal glucose tolerance) subjects (HS) with negative family history of cancer, matched by age, BMI and waist circumference. Peripheral blood mononuclear cells were isolated by means of gradient centrifugation. The K562 human erythroleukemia cell line served as the standard target for human NK cytotoxicity assay. The T2D revealed an increased number of NK cells (13.56 ± 5.9 vs 9.50 ± 4.8 %; p < 0.05) when compared with HS, yet these cells had a decreased activity (3.3 ± 2.5 vs 9.4 ± 3.6 %; p < 0.01). The CC demonstrated a decreased activity (2.9 ± 1.8 %; p < 0.01) but a similar number (8.82 ± 3.7 %; not significant) of NK cells when compared to HS. The T2DCC NK cells were characterized by trace cytotoxic activity (1.1 ± 0.7 %; p < 0.01) and nearly three times greater amount (21.24 ± 7.5 %; p < 0.01) when compared to T2D. Type 2 diabetes and CC are associated with disadvantageous alterations of NK cells, leading to impairment in their cytotoxic activity. The impaired activity of NK cells in T2D can be involved in the increased carcinogenic risk and can promote a higher incidence of CC.

Generation of natural killer cells from hematopoietic stem cells in vitro for immunotherapy

Natural killer (NK) cells are part of the innate immune system and are an alluring option for immunotherapy due to their ability to kill infected cells or cancer cells without prior sensitization. Throughout the past 20 years, different groups have been able to reproduce NK cell development in vitro, and NK cell ontogeny studies have provided the basis for the establishment of protocols to produce NK cells in vitro for immunotherapy. Here, we briefly discuss NK cell development and NK cell immunotherapy approaches. We review the factors needed for NK cell differentiation in vitro, which stem cell sources have been used, published protocols, challenges and future directions for Good Manufacturing Practice protocols.

The role of natural killer cells in hematopoietic stem cell transplantation

Natural killer (NK) cells are important elements of innate immunity, and a large body of evidence supports the significant role of NK in immune surveillance against infections and tumors. Regulation of cytotoxic activity is mediated through activating and inhibitory receptors expressed on the cell surface. NK cells are key players of allogeneic hematopoietic stem cell transplantation (allo-SCT), and previous studies showed the beneficial effect of NK alloreactivity in prevention of relapse, especially in the setting of haploidentical SCT. Biology of human NK cells is an area of active research. Exploitation of the molecular mechanisms regulating NK maturation, tolerance to self, and NK-mediated cytotoxicity will help in the development of innovative NK cell immunotherapy methods.

Use of allogeneic NK cells for cancer immunotherapy

Controversy exists as to the role that the immune system plays in cancer therapy. While the immune system has been proposed to scavenge the body to prevent microscopic transformation from forming cancer, it has been difficult to mount its potential of shrinking established tumors. NK cells are components of the innate immune system. They can recognize targets without prior sensitization, making them ideal candidates to manipulate for therapeutic use against cancer. Initially, autologous NK cells were directed against tumors but it was realized that NK cells that recognize self cells are inhibited. More encouraging advances have been made with allogeneic NK cell therapy in clinical trials to overcome this limitation. In this article, we present developments in NK cell adoptive immunotherapy for hematologic and solid tumor malignancies.

Therapeutic effects of the oriental herbal medicine Sho-saiko-to on liver cirrhosis and carcinoma

The traditional Chinese herbal medicine Sho-saiko-to is a mixture of seven herbal preparations that has long been used in the treatment of chronic liver disease. Various clinical trials have shown that Sho-saiko-to protects against the development of hepatocellular carcinoma in cirrhotic patients. However, the mechanism by which Sho-saiko-to protects hepatocytes against hepatic fibrosis and carcinoma is not yet known. Basic science studies have demonstrated that Sho-saiko-to reduces hepatocyte necrosis and enhances liver function. Sho-saiko-to significantly inhibits hepatic fibrosis by inhibiting the activation of stellate cells, the major producers of collagen in the liver, as well as by inhibiting hepatic lipid peroxidation, promoting matrix degradation, and suppressing extracellular matrix (ECM) accumulation. Furthermore, clinical trials have shown that Sho-saiko-to lowers the rate of hepatocellular carcinoma (HCC) development in patients with cirrhosis and increases the survival of patients with HCC. Unfortunately, some case reports have shown the side effects of Sho-saiko-to. Most of the side effects were interstitial pneumonia and acute respiratory failure induced by Sho-saiko-to in Japan. As a result of analyzing these case reports, the incidence and risk are increased by co-administration of interferon, duration of medication, and, high in an elderly population. This review discusses the properties of Sho-saiko-to with regards to the treatment of chronic liver diseases and suggests the side effects of Sho-saiko-to.

Uterine natural killer (uNK) cells and their missions during pregnancy: a review

Natural killer (NK) cells are lymphocytes of the innate immune system. The aim of this review is to describe the properties and roles of NK cells in the human uterus during pregnancy. Uterine natural killer cells (uNK) constitute a major lymphocyte population during early gestation in the uterus. The uterine natural killer cells are recognized owing to their CD56(bright), CD16(-), CD3(-) phenotype. Their number increases in the first trimester with a subsequent decline as pregnancy progresses. They have been shown to be closely associated with cells of the extravillous trophoblast (EVT) and spiral arteries. They play important roles in remodeling of the spiral arteries, control of trophoblast invasion and in the development of the placenta. Some studies have shown the number and repertoire of receptors of uNK differ between women with healthy pregnancies and those with pathologic pregnancies, such as pre-eclampsia or intrauterine growth retardation. During pregnancy, the cytotoxic characteristics of the uterine killer cells are not directed towards the fetus, and scientists continue to question and explore this phenomenon with increasing evidence that these cells may perform differing beneficial roles during pregnancy. Contrary to their previously suspected "hostile" characteristics, the uterine killer cells are considered to be "friendly" and appear to be essential and very important regulators of successful implantation and pregnancy.

Innate immune natural killer cells and their role in HIV and SIV infection

The findings that early events during HIV-1 and SIV infection of Asian rhesus macaques dictate the levels of viremia and rate of disease progression prior to the establishment of mature and effective adaptive immune responses strongly suggest an important role for innate immune mechanisms. In addition, the fact that the major target of HIV and SIV during this period of acute infection is the gastrointestinal tissue suggests that whatever role the innate immune system plays must either directly and/or indirectly focus on the GI tract. The object of this article is to provide a general overview of the innate immune system with a focus on natural killer (NK) cells and their role in the pathogenesis of lentivirus infection. The studies summarized include our current understanding of the phenotypic heterogeneity, the putative functions ascribed to the subsets, the maturation/differentiation of NK cells, the mechanisms by which their function is mediated and regulated, the studies of these NK-cell subsets, with a focus on killer cell immunoglobulin-like receptors (KIRs) in nonhuman primates and humans, and finally, how HIV and SIV infection affects these NK cells in vivo. Clearly much has yet to be learnt on how the innate immune system influences the interaction between lentiviruses and the host within the GI tract, knowledge of which is reasoned to be critical for the formulation of effective vaccines against HIV-1.

Identification of new populations of chicken natural killer (NK) cells

Natural killer (NK) cell activity is conserved throughout vertebrate development, but characterization of non-mammalian NK-cells has been hampered by the absence of specific mAbs for these cells. Monoclonal antibodies were generated against in vitro IL-2 expanded sorted CD3-CD8alpha+ peripheral blood lymphocytes, previously described to contain chicken NK-cells. Screening of embryonic and adult splenocytes with hybridoma supernatants resulted in five candidate NK markers. Activation of chicken NK-cells with PMA/Ionomycin or with the NK target cell-line LSCC-RP9 resulted in increased expression of CD107 (LAMP-1) and a newly developed flow cytometry based cytotoxicity assay showed that NK-cells were able to kill target cells. Combining NK markers with functional assays indicated that marker positive cells showed NK-cell function. In conclusion, we generated new monoclonal antibodies and developed two functional assays which will enhance our understanding of the role of NK-cells in healthy and diseased chickens.

Role of NK and NKT cells in solid organ transplantation

In the context of solid organ transplantation, the exact interactions between the innate and adaptive alloimmune response have not yet been fully explored. In this transplant setting, natural killer (NK) cells have emerged as a particular focus of interest because of their ability to distinguish allogeneic major histocompatibility complex (MHC) antigens and their potent cytolytic activity. Based on this observation and its potential clinical relevance, NK cells have recently been shown to participate in the immune response in both acute and chronic rejection of solid organ allografts. Numerous experimental and clinical studies demonstrate that NK cells determine transplant survival by rejecting an allograft not directly but indirectly by providing bystander effects. In addition, NK cells are influenced by immunosuppressive therapies such as calcineurin inhibitors or steroids. As NK and natural killer T (NKT) cells have also been shown to play a profound role in allograft tolerance induction, this review summarizes the major findings to highlight the functional role of these lymphocyte subsets, which may constitute an underestimated mechanism affecting graft outcome in solid organ transplantation.

Mixed chimerism to induce tolerance: lessons learned from nonhuman primates

The mixed chimerism approach has been demonstrated to be an effective means of inducing allograft tolerance. Based on our rodent studies on mixed chimerism, we previously developed a clinically relevant nonmyeloablative preparative regimen that permits the induction of mixed chimerism and renal allograft tolerance following donor bone marrow transplantation in major histocompatibility complex fully mismatched cynomolgus monkeys. This approach has been successfully extended to HLA matched or mismatched kidney transplant recipients. In the manuscript, we summarize some of the important conclusions made in our laboratories regarding induction of mixed chimerism and allograft tolerance in a nonhuman primate model.

Human natural killer cells

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

Application of cryo-compatible antibodies to human placenta paraffin sections

The hepes-glutamic acid buffer-mediated organic solvent protection effect (HOPE) -fixation and paraffin embedding technique has been described to expand possibilities for immuno-labellings due to low denaturation of proteins. In this study, the issue was addressed as to whether the HOPE technique could be a useful tool in placenta tissue-based studies when only cryo-compatible antibodies are available. Such antibodies can be used on cryostat sections only, giving results of considerably inferior morphological detail as compared to routinely fixed paraffin embedded tissue sections. Commercially available, only cryo-compatible, monoclonal antibodies against a conformational epitope of HLA-G (clone MEM-G/9) and leukocyte differentiation antigens CD56, CD163 and CD34 III were selected and applied to frozen sections, routinely formalin-fixed and HOPE-fixed paraffin sections. All tested antibodies immunolocalized their antigen on cryo sections and on HOPE-fixed but not formalin-fixed paraffin sections. The HOPE technique provides an excellent preservation of protein antigenicity together with well presented morphological details in paraffin embedded placenta tissues. The detection of native or conformation-dependent epitopes in paraffin sections expands the immunolocalization possibilities in placenta research and reproductive immunology.

Expression and role of phosphatidylcholine-specific phospholipase C in human NK and T lymphocyte subsets

We recently reported evidence of phosphatidylcholine-specific phospholipase C (PC-PLC) involvement in NK cell-mediated cytotoxicity and in lytic granule exocytosis. In the present study, different subpopulations of human PBL were investigated in relation to PC-PLC enzyme expression. While a substantial intracellular amount of PC-PLC was detected in all lymphoid subsets, expression of this enzyme on the outer membrane surface reached high levels only in NK cells, was present at low levels in B lymphocytes and in some TCR gamma/delta T cells and was practically absent in CD4(+) and CD8(+ )T lymphocytes. Moreover, in NK cells two different subpopulations were identified, CD56(dim) PC-PLC(bright) and CD56(bright) PC-PLC(low/-) cells, corresponding to distinct subsets with cytolytic and immunoregulatory functions, respectively. Interestingly, the PC-PLC expression level on the NK membrane surface correlated closely with that of the CD16 receptor, suggesting a possible relationship between enzyme externalization and NK cell maturation. In summary, our results suggest that a high PC-PLC expression on the cell membrane surface of PBL is a peculiarity of NK cytolytic cells, in which the enzyme is apparently involved in the ability of this subset to lyse sensitive target cells.

Mutual interference of HIV and natural killer cell-mediated immune response

Natural killer (NK) cells represent important early effector cells in innate immune defense as they exert their functions without prior sensitization. They participate in regulation of innate and adaptive immune responses and hematopoiesis by producing various cytokines and chemokines. In addition, NK cells lyse virally infected and malignant cells raising them to multifunctional members of the first line of defense. Unlike other lymphocytes they lack specific antigen receptors. They rather bind cells using ubiquitous molecules and communicate via a pattern of receptors specific for MHC-I molecules with their counterparts. In general, successful binding of the receptors delivers an inhibitory signal to NK cells thus sparing the target cell from lysis. In contrast, down-regulated or altered MHC-I expression as frequently observed during virus infection or on malignant cells prevents ligation of inhibitory receptors and MHC-I paralyzing inhibition and thus inducing lysis of the target cell. In human immunodeficiency virus (HIV) infection NK cells are of central importance since they can combat viral infection itself and opportunistic pathogens like fungi and protozoa that usually spread during the course of HIV infection. However, various studies have reported alterations in HIV patients affecting NK cell numbers and functions that might negatively influence course and severity of the disease. This review will focus on the mutual interference of NK cells and the HI virus.

Cytotoxic perforin+ and TIA-1+ infiltrates are associated with cell adhesion molecule expression in dilated cardiomyopathy

OBJECTIVE

To phenotypically characterize cytotoxic T-lymphocytes (CTLs: Perforin+ and TIA-1+ phenotypes) and to study the interactions with cell adhesion molecules (CAMs) in dilated cardiomyopathy (DCM).

BACKGROUND

DCM is linked to intramyocardial inflammation, being characterized by T-lymphocytic infiltration and CAMs abundance. However, the pathogenic significance of increased CD3+ lymphocytes remains obscure as these do not correlate with CTLs (perforin+ and TIA1+ phenotypes). CAMs participate in the phenotypic repertoire and effector pathways of CTLs.

METHODS

CAMs-expression (ICAM-1, VCAM-1, LFA-3, CD29, CD62E and CD62P and beta(2)-integrins), CD3+ (T-lymphocytes), CD57+ (NK-cells) and adhesion related (CD18+, CD11a+, CD11b+, CDw49d+) phenotyped infiltrates were investigated in endomyocardial biopsies (EMBs) from 89 DCM patients (33 female; LVEF<40%) using immunohistochemisty. The enteroviral genome was identified by nested RT-PCR.

RESULTS

CAMs abundance was confirmed in 55 DCM patients (62%) and 29 EMBs (33%) were graded CTLs+ (>1.5 TIA-1+ and/or >2.0 perforin+ infiltrates/hpf). CTLs correlated with all endothelial CAMs-markers studied (P<0.01), the adhesion related phenotypes of infiltrates (LFA-1, VLA-4, CD18) and CD57+ NK-cells (P<0.02). There was no correlation of CTLs with CD3+ T-lymphocytes, CD11b+ macrophages, enteroviral infection (present in n=16/18%), clinical history and LVEF (P>0.05). Phenomena suggestive of CTLs mediated myocytolysis were observed in 10 patients (11%).

CONCLUSIONS

CTLs-infiltrates are associated with endothelial CAMs-abundance and co-express adhesion related (beta2-integrins, VLA-4) and NK-cellular antigens (CD57) in DCM. Endothelial CAMs expression also reflects cytotoxic activation of intramyocardial infiltrates, which is not reflected by immunologically nai;ve CD3 T-lymphocytes.

Uncoupling activation-induced modulation of CD16 and CD69 in CD56+ cells during AIDS

The immune system of HIV+ patients is chronically activated, which has been associated with a detrimental effect on both innate and acquired immunity during AIDS. We analyzed the expression and modulation of the triggering markers CD69 and CD16 in CD56+ cells from 18 asymptomatic HIV+ individuals and 8 AIDS patients, compared with 21 seronegative subjects. We observed a diminished PMA-induced CD16 downregulation in AIDS patients (p<0.01), associated with low numbers of CD4+ cells (p<0.02). Furthermore, an enhanced unstimulated expression of CD69 in asymptomatic HIV+ patients (p<0.05) was shown. AIDS patients could not efficiently upregulate PHA-dependent CD69 expression (p<0.05), which correlated with low CD4+ counts (p< 0.05). These abnormalities in CD16 and CD69 modulation were recorded in patients under highly active antiretroviral therapy (HAART). Our results demonstrate an altered modulation of two functionally relevant receptors in CD56+ cells from AIDS patients, contributing to our understanding of the immunopathogeny of NK cell dysfunction during disease progression.

CD56bright cells differ in their KIR repertoire and cytotoxic features from CD56dim NK cells

In this study we present new differential characteristics of NK cells expressing CD56 surface antigen in low (CD56dim) or high (CD56bright) density. In contrast to CD56bright NK cells CD56dim cells express killer cell immunoglobulin (Ig)-like receptors (KIR) such as CD158a, CD158b, and NKB1. However, c-type lectin-like receptors (KLR) CD94/NKG2 and CD161 are present on both subsets. The ability to form conjugates with susceptible targets is approximately twice as strongly pronounced in CD56dim vs. CD56bright NK cells. Last but not least, granules of CD56dim cells contain about tenfold more perforin and granzyme A enabling potentially more effective cytolysis compared to CD56bright NK cells. On the other hand, CD56bright NK cells are superior in producing the proinflammatory cytokines IFN-gamma (28.5% vs. 20.8%, p<0.05) and TNF-alpha (28% vs. 15.8%, p<0.001). The different NK cell populations retained their specific phenotype in vitro during culture in the presence of IL-2 contradicting that they simply display different stages of maturity. Taken together our data support the view that CD56bright cells are specialized NK cells that regulate immunological response mechanisms rather by cytokine supply than by their cytotoxic potential. The poor cytolytic capacity of CD56bright NK cells can be explained by weak ability in forming conjugates with target cells and low contents of perforin and granzyme A in their granules.

CD56bright cells differ in their KIR repertoire and cytotoxic features from CD56dim NK cells

In this study we present new differential characteristics of NK cells expressing CD56 surface antigen in low (CD56dim) or high (CD56bright) density. In contrast to CD56bright NK cells CD56dim cells express killer cell immunoglobulin (Ig)-like receptors (KIR) such as CD158a, CD158b, and NKB1. However, c-type lectin-like receptors (KLR) CD94/NKG2 and CD161 are present on both subsets. The ability to form conjugates with susceptible targets is approximately twice as strongly pronounced in CD56dim vs. CD56bright NK cells. Last but not least, granules of CD56dim cells contain about tenfold more perforin and granzyme A enabling potentially more effective cytolysis compared to CD56bright NK cells. On the other hand, CD56bright NK cells are superior in producing the proinflammatory cytokines IFN-gamma (28.5% vs. 20.8%, p<0.05) and TNF-alpha (28% vs. 15.8%, p<0.001). The different NK cell populations retained their specific phenotype in vitro during culture in the presence of IL-2 contradicting that they simply display different stages of maturity. Taken together our data support the view that CD56bright cells are specialized NK cells that regulate immunological response mechanisms rather by cytokine supply than by their cytotoxic potential. The poor cytolytic capacity of CD56bright NK cells can be explained by weak ability in forming conjugates with target cells and low contents of perforin and granzyme A in their granules.

Deficiency in circulating natural killer (NK) cell subsets in common variable immunodeficiency and X-linked agammaglobulinaemia

Absolute and relative NK cell numbers were determined in peripheral whole blood by flow cytometry in patients with common variable immunodeficiency (CVID) (n = 55) and X-linked agammaglobulinaemia (XLA) (n = 19) on regular immunoglobulin (IVIG) therapy. Absolute CD3-CD16+ NK cell numbers were significantly reduced in CVID patients (median 108/microl, range 23-815), compared with normal subjects (n = 60) (289/microl, range 56-640, P < 0.001). Total lymphocyte concentrations were significantly lower in CVID (median 1587/microl, range 523-7519) compared with normal subjects (median 2019/microl, range 1124-3149, P = 0.004), with the percentage of NK cells also being significantly decreased (median 7.5%, range 3.0-33. 0%, compared with 14.2%, range 2.6-30.8%, P < 0.001). In XLA, absolute NK cell numbers (median 140/microl, range 32-551, P < 0. 001) but not relative numbers were significantly reduced compared with normal controls. We excluded the possibility that IVIG interferes with in vitro binding of CD16 MoAbs. Further analysis of NK cell subsets showed a deficiency of both CD16+ and CD56+ cells in CVID, most marked in the CD3-CD8dim subpopulation, which may be due to increased homing of these cells to the gut. Serial studies on a small number of patients suggest that IVIG therapy has no short-term effect on NK cells, although we cannot exclude an effect with prolonged use. Although there are no obvious clinical effects of the NK depletion in CVID and XLA, this may be a factor in their predisposition to cancer.

Reconstitution of NK cell activity in HIV-1 infected individuals receiving antiretroviral therapy

We studied natural immunity mediated by natural killer (NK) cells in 62 HIV-1 infected individuals, 54 HIV-1 infected individuals receiving highly active antiretroviral therapy (HAART) for more than one year and 8 HIV-1 infected individuals without antiretroviral therapy. 22 individuals had a complete suppression of viral replication characterized by viral load values <50 copies/ml, whereas 32 individuals presented with persistent viral replication. The 8 untreated patients had an indication to start antiretroviral treatment. Lytic activity of NK cells was measured in a 51chromium release assay. In patients with persistent viral replication under HAART NK cell activity was significantly decreased compared to patients with effective control of HIV viremia. Patients with complete suppression of HIV replication displayed a similar NK activity to healthy control persons. Differences in antibody-dependent cellular cytotoxicity (ADCC) were not observed. Further studies will investigate whether decreased NK cell activity is a reason for or the consequence of persistent viral replication.

CMV complications in common variable immunodeficiency

A patient suffering from common variable immunodeficiency is described, who developed a myelitis under treatment with glucocorticosteroids. Later on, autoimmune complications had to be treated with azathioprine. An exacerbation of the myelitis, retinitis, encephalitis and colitis was observed and a cytomegalovirus infection diagnosed. This infection does not represent a typical complication of common variable immunodeficiency. A functional NK cell defect was detected that may contribute to susceptibility for cytomegalovirus infection in addition to immunosuppressive therapy.

Reduced IL-12 level correlates with decreased IFN-gamma secreting T cells but not natural killer cell activity in asthmatic children

BACKGROUND

Accessory cells such as macrophages and natural killer cells, and their cytokines such as IL-10, IL-12, and IFN-gamma have been suggested to play a critical role in the development of T helper cells.

OBJECTIVE

Both natural killer cells and peripheral blood mononuclear cells were isolated and stimulated for their ability in producing cytokines. In addition, the percentage of IFN-gamma-secreting cells was analyzed with the method of intracellular staining.

RESULTS

The data suggested (1) no significant difference between asthmatic children and normal controls in number, cytotoxicity, and IFN-gamma production of purified NK cells; (2) decreased secretion of IL-12 by stimulated peripheral blood mononuclear cells in asthmatic children compared with normals (P < .05); (3) decreased production of IFN-gamma by PBMC from asthmatic children compared with normals (P < .05); and (4) intracellular expressed IFN-gamma level was lower in CD4+ T cells of asthmatic children (P < .05).

CONCLUSION

The results suggested that IL-12 produced predominantly by macrophages and associated decreased IFN-gamma-secreting CD4+ T cells play a critical role in the pathogenesis of asthma.

Effect of interleukin (IL)-12 and IL-15 on activated natural killer (ANK) and antibody-dependent cellular cytotoxicity (ADCC) in HIV infection

The ability of IL-12 and IL-15 to enhance natural killer (NK) activity and antibody-dependent cellular cytotoxicity (ADCC) of mononuclear cells (MNCs) from HIV+ children and their mothers was investigated. MNCs from HIV+ patients were deficient in NK and ADCC activity compared to control MNCs against several target cells. Overnight incubation with IL-15 or IL-12 augmented NK activity of MNCs from both patients and controls, and the combination of IL-12 and IL-15 resulted in the greatest enhancement. ADCC in HIV+ patients against gp120-coated CEM.NKR cells or chicken erythrocytes could also be enhanced by IL-2 or IL-15 in overnight cultures. Culturing MNCs with either IL-2 or IL-15 for 1 week increased the NK activity in patients to levels of controls treated with these cytokines. However, the response to the combination of IL-12 and IL-15 was less than that to IL-15 alone in 1-week cultures. Culturing MNCs with IL-2 and IL-15 for 1 week also increased the percentage of CD16+/CD56+ cells in both patients and controls. Thus, IL-15 can restore the deficient NK activity in patients and may be a candidate for immunomodulative therapy in HIV+ patients.

MHC-I antigen expression determines sensitivity of hematopoetic progenitor cells as targets for NK cells

Hybrid resistance is suggested to be mediated by NK lymphocytes as effector cells. NK cytotoxicity is triggered by specific NK cells receptors. One group of receptors recognizing MHC-I antigens is predominantly transmitting an inhibitory signal into the cell. However, NK cells have not been shown to recognize hematopoetic progenitor cells directly. In these studies we demonstrate that hematopoetic progenitor cells are sensitive targets for NK recognition. NK cytotoxicity is shown to depend on MHC-I antigen expression on these target cells. Bone marrow-derived hematopoetic progenitor cells from a beta 2-microglobulin-deficient mouse strain exhibit a significant increase of cytotoxic susceptibility compared with the wild type control. CFU-assays reveal an almost complete loss of proliferation after coincubating MHC-I-deficient bone marrow cells with NK cells from the wildtype mouse strain. The examination of H-2K in allorecognition of hematopoetic progenitor cells reveals an increased cytotoxicity after treatment of resistant syngeneic hematopoetic progenitor cells with H-2Kb F(ab)2-antibodies. Also masking of allogeneic hematopoetic progenitor cells with anti-H-2Kd F (ab)2-antibodies results in enhanced NK killing. Thus, hematopoetic progenitor cells are sensitive targets for NK cells and MHC-I antigen complex is the critical structure in NK recognition of hematopoetic progenitor cells. This complex mediates resistance of NK-specific lysis of hematopoetic progenitor cells.

Interleukin-2-activated killer cell activity in colorectal tumor patients: evaluation of in vitro effects by prothymosin alpha1

The effects of prothymosin alpha1 (Pro alpha1) in combination with interleukin-2 (IL-2) on peripheral blood lymphocytes from 50 colorectal tumor patients at different stages were studied with respect to immunocytotoxicity, adhesion to cultured SW620 colon carcinoma cells, secretion of cytokines and expression of adhesion and surface marker molecules. On average, the patients showed lower natural killer (NK) cell activity than healthy donors, which was associated with a lower adhesion capacity to the tumor target cells. The NK cell activity of the patients was inversely related to the tumor stage. The generation of lymphokine(IL-2)-activated killer (LAK) cell activity was found to be comparable on lymphocytes from healthy individuals and patients and was not correlated to tumor stage. Pro alpha1 stimulated patients' LAK cell activity only, primarily at the early stage (Dukes A/B). The Pro alpha1 effect was associated with an increased adhesion of lymphocytes to tumor target cells and an increased secretion of the deficient IL-2-induced IFN gamma secretion. No significant effects on the low level of TNF alpha secretion was noted. By flow cytometry, Pro alpha1 in combination with IL-2 augmented the expression of the NK cell markers CD56, CD16/56, the subset CD3/16/56 and CD25 on lymphocytes of the patients. In contrast, Pro alpha1 was equally effective by increasing the expression of CD18 and CD11a on lymphocytes from the patients and from normal controls. In conclusion, Pro alpha1, in combination with IL-2, can partially normalize lymphocyte deficiencies of colon cancer patients in vitro. This potential might provide an experimental basis for applying Pro alpha1 or related thymic peptides in selected immunotherapies against colorectal tumors.

Clonal Proliferation and Cytokine Requirement of Murine Progenitors for Natural Killer Cells

We have established a clonal cell culture system that supports the proliferation of committed natural killer (NK) cell progenitors of mice to investigate the pathway and cytokine regulation of NK cell development. Day 14 fetal thymocytes cultured in methylcellulose with interleukin-7 (IL-7), IL-15, and steel factor (SF ) formed diffuse colonies that could not be classified to known colony types. Single-cell origin of the colonies was established by micromanipulation of the colony-forming cells. Cells in the colonies are very blastic, showing no cytoplasmic differentiation, and express Ly5, Thy-1, and CD25 but not myeloid, B, mature T, or NK cell markers. The cells lack T, B, and myeloid potentials but can differentiate to mature NK cells in fetal thymus organ culture, suggesting that the colonies consist of NK committed progenitors. Examination of the minimal cytokine requirement for the NK colony formation showed that IL-7 and SF are indispensable for the formation of immature NK cell colonies. Both IL-2 and IL-15 increased the frequency of colonies. In contrast to IL-2, IL-7, and IL-15, IL-4 strongly inhibited the formation of the colonies. This quantitative clonal culture will provide a useful means to examine the mechanism of NK cell development.

Lymphoblastic lymphoma expressing natural killer cell phenotype with involvement of the mediastinum and nasal cavity

Most CD56+ lymphomas display polymorphic and angiocentric/angiodestructive histologic features and are closely related to Epstein-Barr virus (EBV) infection. We report a 47-year-old Japanese man with CD56+ lymphoma that showed histologic features of lymphoblastic lymphoma with mediastinal and nasal involvement and an aggressive course. A sample specimen showed the histology of lymphoblastic lymphoma with a positive reaction for terminal deoxynucleotidyl transferase (TdT) but no angiocentric/angiodestructive features. Transmission electron microscopy revealed a few membrane-bound electron-dense granules in their cytoplasm. Immunohistochemically, lymphoma cells exhibited CD56+ cytoplasmic CD3 (cCD3)+ TdT+. A Southern blot analysis showed no integration of EBV and human T-lymphotrophic virus 1 (HTLV-1) and no rearrangement of the T-cell receptors or immunoglobulin heavy chain genes. This unusual lymphoblastic lymphoma exhibiting cCD3 + CD56 + TdT + TCR- is assumed as an immature or progenitor natural killer cell lineage.

Distinct Ca2+ response patterns in human natural killer cells during induction of necrosis or apoptosis of target cells

Human CD3-, CD16+ natural killer cells (NKs) induced necrosis in the cell line K562 and the minor population of MOLT-4, while induced apoptosis in the majority of MOLT-4, in one-to-one cell interaction. Simultaneous Ca2+ imaging of NK and target cells revealed remarkable differences in changes of cytosolic Ca2+ concentration ([Ca2+]i) during the process of distinct target cell killing. A rapid [Ca2+]i rise in NK was generated within 2 min after contact with any target. For induction of necrosis, the [Ca2+]i rise in NK reached a peak of 580 +/- 195 nM (mean +/- SD, n = 41) and was followed by an abrupt large [Ca2+]i rise in target cells probably due to Ca2+ entry through pores formed by perforin which was released from NK. The interval between onsets of NK and target Ca2+ responses (Tnk-t) was shorter than 3 min in most cases. Target cells were soon permeabilized, and NK Ca2+ responses ceased in 14 +/- 7 min. For induction of apoptosis, NK Ca2+ responses were relatively smaller (405 +/- 125 nM, n = 16), and Tnk-t was widely scattered up to 30 min. NK Ca2+ responses lasted much longer in a form of Ca2+ oscillations (total duration, 66 +/- 33 min) in parallel with target Ca2+ responses, and ceased as apoptotic changes such as cellular and nuclear fragmentation advanced. The difference in Tnk-t suggests that rapid synchronous release of perforin tends to cause necrosis rather than apoptosis. The duration of NK Ca2+ responses suggests that some 'off signals' may be transmitted to NK following recognition of target cell damage.

Natural killer cells and cancer

BACKGROUND

Natural cytotoxicity, mediated by natural killer (NK) cells and cell with lymphokine-activated killer (LAK) activity, is believed to play an important role in host anti-cancer mechanisms.

METHODS

The authors critically review recent publications on the role of natural cytotoxicity in patients with cancer.

RESULTS

In patients with cancer, several studies have noted variations in the numbers and activity of NK and cells with LAK activity in different body compartments. NK cell activity in the peripheral blood lymphocytes (PBLs) is higher than that found in lymph nodes and within tumors, and this appears to be due to the presence of suppressor factors. The natural cytotoxicity of PBLs in patients with different types of cancers varies. However, there appears to be a trend for natural cytotoxicity to be reduced in certain cancer patients, possibly related to tumor volume or dissemination. Anti-cancer treatments (e.g., surgery, hormonal modulation, radiotherapy and chemotherapy) can also result in suppression of natural cytotoxicity, although the long-term effect on response to treatment and development of metastases is at present unknown.

CONCLUSIONS

NK and LAK cells, through the use of immune biologic modifiers, have been demonstrated to have a therapeutic role in the treatment of human cancers. Further studies are required to determine the optimal dosages and combinations of chemotherapeutic agents, the timing of surgery, and the adjuvant use of immune biologic response modifiers. An increasing awareness and understanding of this field, may allow for the future development of anti-cancer therapies.