Functional activity of natural killer cells and killer T cells in mice after ovarian transplantation

Tashkent Postgraduate Medical Institute, Ministry of Health of the USSR. (Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Lopatkin). Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 112, No. 9, pp. 273–275, September, 1991.     

Brief report: killer cell defect and persistent immunological abnormalities in two patients with chronic active Epstein-Barr virus infection

Two members of a family have manifested a syndrome of chronic active Epstein-Barr virus (EBV) infection. A father and his daughter suffered prolonged or recurrent mononucleosis, with splenomegaly, anemia, and intermittent fever; persistent immunological abnormalities included defective natural killer (NK) cytotoxicity, inverted CD4/CD8 ratios, hyper IgG1, high EBV viral capsid antigen (VCA) and early antigen (EA) antibodies, and low or undetectable EBV nuclear antigen (EBNA) antibody titers. The EBV seronegative member of the family was free of these abnormalities. However, NK activity in the seronegative individual was low-normal and its EBV-specific antibody-dependent K-cell cytotoxicity (EBV-ADCC) was abnormally low, suggesting that this K-NK cell defect may be primary. The father, who suffered from the syndrome for more than 15 years, lacked (or lost) antibodies to EBV-envelope and infected cell membranes, such as antibody-dependent cellular cytotoxicity (ADCC), neutralizing (NT), and gp 350/220 antibodies. Slow improvement over a period of years was heralded by rising NK cytotoxicity.     

Expression of natural killer cell activating receptors in patients with chronic lymphocytic leukaemia

Recent advances in chronic lymphocytic leukaemia (CLL) treatment, more particularly through upfront use of anti-CD20 monoclonal antibodies, have prolonged patient progression-free survival. Nonetheless, apart from allogeneic stem cell transplantation, no curative treatment is available. One possible explanation for the lack of cure in CLL could be a defective immune anti-tumour response. As the result of abnormal HLA class I molecule expression, CLL cells escape from specific T-lymphocyte immunity but should be the target for the innate natural killer (NK) cell-mediated immune response. Defective NK cytotoxicity as the result of decreased expression of the natural cytotoxicity receptors (NCRs) NKp30/NCR3, NKp44/NCR2 and NKp46/NCR1 has been described in haematological malignancies such as acute myeloid leukaemia. This prompted us to focus our attention on NCR expression on NK cells from patients with CLL. Although we failed to detect any difference between CLL patients and healthy age-matched controls, a precise analysis of clinical data showed a correlation between decreased NCR expression and poor prognosis factors such as low haemoglobin level, high (>30×10(9) per litre) lymphocyte count or elevated C-reactive protein. Together, these observations support the rationale for restoration of normal NK cell functions in patients with CLL, putatively through the use of immune therapy protocols that already have demonstrated some benefit in acute myeloid leukaemia such as interleukin-2 plus histamine dihydrochloride.     

Azathioprine suppression of natural killer activity and antibody-dependent cellular cytotoxicity in renal transplant recipients

The relative effects of azathioprine (AZA) and prednisone (PRED) on natural killer (NK) activity and the antibody-dependent cellular cytotoxicity (ADCC) of K (killer) cells and the number of FcR and other lymphoid cells were examined in renal transplant recipients. In addition to both long-term (>6 months) and short-term (<6 months) transplant recipients receiving conventional AZA-PRED therapy, an important group of long-term recipients receiving PRED but not AZA was studied for the first time. Both NK activity and ADCC are profoundly reduced in the long-term AZA-PRED group but are normal in the long-term PRED-alone (no-AZA) group. The short-term AZA-PRED group exhibits NK and ADCC levels significantly lower than normal but not as low as those of the long-term AZA-PRED group. Patient groups with low NK and ADCC also have low circulating Fc receptor-bearing (FcR) cells. A single patient in the long-term AZA-PRED group was removed from AZA therapy, and approximately 3 months was required for the patient's suppressed NK and ADCC to return to normal. These findings indicate that AZA rather than PRED is the major drug important in suppressing ADCC and NK activity in renal transplant recipients. Several months are required for combination AZA-PRED therapy to reduce these cytotoxic activities. Similarly, several months are required for suppressed ADCC and NK activity to return to normal upon discontinuation of AZA.     

Intrahepatic and peripheral blood phenotypes of natural killer and T cells: differential surface expression of killer cell immunoglobulin‐like receptors

Deep characterization of the frequencies, phenotypes and functionalities of liver and peripheral blood natural killer (NK), natural killer T (NKT) and T cells from healthy individuals is an essential step to further interpret changes in liver diseases. These data indicate that CCR7, a chemokine essential for cell migration through lymphoid organs, is almost absent in liver NK and T cells. CD56^bright NK cells, which represent half of liver NK cells, showed lower expression of the inhibitory molecule NKG2A and an increased frequency of the activation marker NKp44. By contrast, a decrease of CD16 expression with a potential decreased capacity to perform antibody‐dependent cellular cytotoxicity was the main difference between liver and peripheral blood CD56^dim NK cells. Liver T cells with an effector memory or terminally differentiated phenotype showed an increased frequency of MAIT cells,T‐cell receptor‐γδ (TCR‐γδ) T cells and TCR‐αβ CD8⁺ cells, with few naive T cells. Most liver NK and T cells expressed the homing markers CD161 and CD244. Liver T cells revealed a unique expression pattern of killer cell immunoglobulin‐like receptors (KIR) receptors, with increased degranulation ability and higher secretion of interferon‐γ. Hence, the liver possesses a large amount of memory and terminally differentiated CD8⁺ cells with a unique expression pattern of KIR activating receptors that have a potent functional capacity as well as a reduced amount of CCR7, which are unable to migrate to regional lymph nodes. These results are consistent with previous studies showing that liver T (and also NK) cells likely remain and die in the liver.     

Effect of vernolide-A,a sesquiterpene lactone from Vernonia cinerea L., on cell-mediated immune response in B16F-10 metastatic melanoma-bearing mice

One of the major reasons for the rapid progression of cancers is the ability of tumor cells to escape from the immune surveillance mechanism of the body. Modulation of immune responses is highly relevant in tumor cell destruction. Effect of vernolide-A on the cell-mediated immune (CMI) response in metastatic condition was studied using C57BL/6 mice model. Administration of vernolide-A enhanced natural killer (NK) cell activity, antibody-dependent cellular cytotoxicity (ADCC), and antibody-dependent complement-mediated cytotoxicity (ACC) and the activity was observed in treated group much earlier compared with the metastatic tumor-bearing control. Administration of vernolide-A significantly enhanced the production of interleukin (IL)-2 and interferon-gamma (IFN-γ) in metastatic tumor-bearing animals. In addition, vernolide-A significantly down-regulated the serum levels of proinflammatory cytokines such as IL-1β, IL-6, tumor necrosis factor-alpha (TNF-α), and granulocyte–macrophage colony-stimulating factor (GM-CSF) during metastasis. All these results demonstrate that vernolide-A could enhance the immune response against metastatic progression of B16F-10 melanoma cells in mice.     

Cytotoxicity of human natural killer (NK) cell subsets for Plasmodium falciparum erythrocytic schizonts: stimulation by cytokines and inhibition by neomycin.

Quantification of human peripheral blood NK subsets has been made in a group of Kenyan adults and children with acute P. falciparum malaria. Results were compared with data obtained from three age- and sex-matched control cohorts: parasitaemic but asymptomatic children; aparasitaemic children and adults; and adult Caucasians with no previous history of malaria. Separated NK subsets were tested in vitro for cytotoxicity to erythrocytic schizonts of P. falciparum in the presence and absence of cytokines. There was a statistically significant quantitative and qualitative depression of the CD3-CD56+ subset in patients with acute malaria and this was accompanied by an expansion of the 'non-functional' CD3-CD57+CD16-CD56- subset. Both CD3-CD16+ and CD3-CD56+ NK cells from all patients and donors lysed schizonts, and this cytotoxicity was enhanced by the addition of recombinant interferon-alpha and/or IL-2, notably with the CD3-CD56+ subset. Interestingly, asymptomatic donors had the highest levels of CD3-CD56+ NK cells, which also demonstrated an enhanced response to cytokine stimulation. Cytotoxicity to schizonts was accompanied by the release of soluble NK cell lytic factors. Neomycin suppressed cytotoxicity in a dose-dependent manner, indicating that the lysis of schizonts by NK cells involves phospholipase C-mediated phosphoinositide metabolism. Our findings define a role for NK cells in immunity to malaria through the lysis of infected erythrocytes as a first-line defence against the parasite.     

Frequency and phenotype of natural killer cells and natural killer cell subsets in bovine lymphoid compartments and blood

Natural killer (NK) cells are widely distributed in lymphoid and non‐lymphoid tissues, but little is known about the recirculation of NK cells between blood and tissues. This is relevant to understanding recirculation in the steady‐state and also for determining the roles for NK cells in vaccine‐induced immunity and responses to infection. Therefore, the percentage of NK cells and their phenotype across peripheral blood, afferent lymph and lymph nodes in steady‐state conditions was investigated in cattle using the pseudo‐afferent lymphatic cannulation model. CD2⁺ CD25^lo NK cells were the predominant subset of NK cells within the blood. In contrast, CD2⁻ CD25^hi NK cells were the main subset present within the skin‐draining afferent lymphatic vessels and lymph nodes, indicating that CD2⁻ NK cells are the principal NK cell subset trafficking to lymph nodes via the afferent lymphatic vessel. Furthermore, a low percentage of NK cells were present in efferent lymph, which were predominantly of the CD2⁻ subset, indicating that NK cells can egress from lymph nodes and return to circulation in steady‐state conditions. These compartmentalization data indicate that NK cells represent a population of recirculating lymphocytes in steady‐state conditions and therefore may be important during immune responses to vaccination or infection.     

Functional subsets of mouse natural killer cells

Summary:  Human natural killer (NK) cells can be divided into two phenotypically distinct functional subsets based on their cell surface expression of CD56 (CD56^bright and CD56^dim). As mouse NK cells do not express CD56, comparable mouse NK cell subsets have proven difficult to identify. Recently, we have found that mouse NK cells can be subdivided by the expression of CD27. The CD27^hi and CD27^lo mouse NK cell subsets show some intriguing similarities to but also some distinct differences from the human CD56 NK cell subsets in terms of their function and phenotype. Extending our knowledge of mature NK cell heterogeneity between the species will be critical to further our understanding of the pathological role of NK cells in immune responses.     

Modulation of the natural killer cell KIR repertoire by cytomegalovirus infection

Patients carrying activating killer cell immunoglobulin‐like receptor (KIR) genes are significantly protected from CMV‐associated complications after solid organ or hematopoietic stem cell transplantation. Whether previous infection with CMV affects NK‐cell function in healthy donors is unknown. We studied the KIR repertoire and alterations of KIR expression after in vitro exposure to CMV in 54 healthy donors. The expression of neither activating nor inhibitory KIRs was different at baseline between 23 seropositive and 31 seronegative donors. However, after co‐culture of NK cells with CMV‐infected fibroblast cells, expression of the inhibitory receptors KIR2DL1 and KIR2DL3 and the activating receptor KIR3DS1 significantly increased in CMV‐seropositive donors. In CMV‐seronegative donors, changes were subtle and restricted to the subset of NK cells expressing NK‐cell group antigen 2C (NKG2C). Expansion of inhibitory KIRs occurred exclusively in donors carrying the cognate HLA class I ligands, whereas the presence of the putative ligand HLA‐Bw4 was not necessary for the expansion of KIR3DS1‐expressing NK cells. Our data show that previous infection with CMV does not alter the resting NK‐cell receptor repertoire, but appears to modify how NK cells respond to re‐exposure to CMV in vitro.     

Circulating soluble factor-inhibiting natural killer (NK) activity of fresh peripheral blood mononuclear cells (PBMC) from inflammatory bowel disease (IBD) patients

This study was performed in order to assess the cytotoxic activity, both natural (NK) and antibody-dependent (ADCC), of PBMC from 38 IBD patients and correlate it with their clinical features. Cytotoxicity assays were performed using sensitive target cells for NK and ADCC activities. In some experiments, highly purified NK cells, obtained both by Percoll density gradient and by co-culturing non-adherent PBMC with RPMI 8866 feeder cells, were used as effector cells. Furthermore, we evaluated NK cell parameters such as number, surface expression of adhesion molecules (CD11a/CD18, CD49d and CD54) and response to different stimuli. We observed a decreased NK cytotoxicity of PBMC from IBD patients, both in ulcerative colitis (UC) and Crohn's disease (CD), independently of the clinical activity of disease. In contrast, the ADCC lytic activity was within normal range. The lower NK cytotoxic activity observed in our IBD patients cannot be related to a decreased number of NK cells, surface expression of adhesion molecules, defective response to IL-2 and maturative defect. Decreased NK activity was induced in PBMC of controls when serum of patients was added and this was unrelated to monocyte-derived modulating factor(s). Our data show a decreased natural killing by fresh PBMC from IBD patients. This lower activity seems to be unrelated to a primary NK cell defect, since purified NK cells exhibited normal levels of killing. It might be hypothesized that serum factors, possibly derived from lymphocytes, with inhibitory properties on NK activity, might be functionally active in the blood of IBD patients, thus modulating NK activity.     

Conserved and variable natural killer cell receptors: diverse approaches to viral infections

Natural killer (NK) cells are lymphocytes of the innate immune system with essential roles during viral infections. NK cell functions are mediated through a repertoire of non-rearranging inhibitory and activating receptors that interact with major histocompatibility complex (MHC)–peptide complexes on the surface of infected cells. Recent work studying the conserved CD94–NKG2A and variable killer cell immunoglobulin-like receptor–MHC systems suggest that these two receptor families may have subtly different properties in terms of interactions with MHC class I bound peptides, and in recognition of down-regulation of MHC class I. In this review, we discuss how these properties generate diversity in the NK cell response to viruses.     

Regulation of human natural killer cell activity by an interferon inhibitor

Laboratory of Immunochemistry and Department of Interferons, N. F. Gamaleya Research Institute of Epidemiology and Microbiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 112, No. 10, pp. 395–397, October, 1991.     

Down-regulation of natural killer cell activity by autologous polymorphonuclear leucocytes

It has been recently reported that neutrophils are involved in the regulation of NK cell activity. However, the mechanism of such regulation is unclear. The present study was designed to investigate the mechanisms involved in the regulation of NK cytotoxicity by human neutrophils. The role of indomethacin, an anti-inflammatory drug, in this interaction was studied. NK cells were purified from peripheral blood obtained from normal individuals. NK cell cytotoxicity was tested on K 562 cell line by Cr release assay. Autologous neutrophils obtained from peripheral blood were stimulated by opsonized zymosan either in the presence or absence of indomethacin. The role of neutrophil supernatant containing oxygen radicals and prostaglandins on NK cytotoxicity was examined. It was shown that supernatants from stimulated neutrophils significantly inhibited (P less than 0.05) the autologous NK cell cytotoxicity. The presence of indomethacin in the in vitro reaction mixture, or given orally to donors, partially or completely abolished the inhibitory effect of neutrophil supernatant. Indomethacin inhibited prostaglandin E2 release, and luminol-enhanced, myeloperoxidase-mediated chemiluminescence of activated PMN. Diafiltration of neutrophil supernatant showed that the inhibitory activity was present in the fraction containing molecules lower than 5,000 daltons. In conclusion, our findings indicate that down-regulation of NK cytotoxicity is mediated by prostaglandins produced by stimulated neutrophils and possibly by oxygen radicals.     

The up side of decidual natural killer cells: new developments in immunology of pregnancy

Early phases of human pregnancy are associated with the accumulation of a unique subset of natural killer (NK) cells in the maternal decidua. Decidual NK (dNK) cells that are devoid of cytotoxicity play a pivotal role in successful pregnancy. By secreting large amounts of cytokines/chemokines and angiogenic factors, dNK cells participate in all steps of placentation including trophoblast invasion into the maternal endometrium and vascular remodelling. In this review, we summarize some of dNK cell features and discuss more recent exciting data that challenge the conventional view of these cells. Our new data demonstrate that dNK cells undergo fine tuning or even subvert their classical inhibitory machinery and turn into a real defence force in order to prevent the spread of viruses to fetal tissue. Today it is not clear how these phenotypic and functional adaptations impact cellular cross‐talk at the fetal–maternal interface and tissue homeostasis. Ultimately, precise understanding of the molecular mechanisms that govern dNK cell plasticity during congenital human cytomegalovirus infection should lead to the design of more robust strategies to reverse immune escape during viral infection and cancer.     

Lactoferrin-inducible monocyte cytotoxicity for K562 cells and decay of natural killer lymphocyte cytotoxicity.

Monocyte-enriched and lymphocyte-enriched fractions of peripheral blood from three healthy volunteers were obtained by percoll density gradient centrifugation. The cytotoxic activity of each fraction against 51Cr-labelled K562 cells was quantified in a 2-h assay using freshly isolated cells of each fraction and cells of each fraction which had been incubated with and without lactoferrin in complete medium for 18 h before performing the assay. We have thereby shown that cytotoxicity was not demonstrable in the lymphocyte fraction (containing 7.3 +/- 2% large granular lymphocytes) after 18 h in medium, whereas the cytotoxicity of the monocyte fraction (containing 3 +/- 0.4% large granular lymphocytes) was still significantly increased (P less than or equal to 0.01) and that lactoferrin had no effect on lymphocyte fraction cytotoxicity while producing an 11-fold increase in the cytotoxicity of the monocyte fraction. It is therefore possible to perform a relatively simple test of monocyte cytotoxicity using lactoferrin as a stimulant in a 2-h 51Cr-labelled K562 assay system by allowing 18 h to elapse for lymphocyte natural killer cytotoxicity to decay.