Molecular analysis and solution structure from small-angle X-ray scattering of the human natural killer inhibitory receptor IRp60 (CD300a)

Natural killer (NK) cells are lymphocytes of the innate immune system specialized in recognition and killing of certain virus-infected and tumor cells. To carry out this task, NK cells are equipped with a complex array of germ line encoded receptors. These receptors deliver either positive or negative signals, and a delicate balance between these signals governs the NK cell cytolytic activity against the target cell. IRp60 (CD300a) is a human NK inhibitory receptor with an immunoglobulin-like fold. In the present study the IRp60 protein was expressed in Escherichia coli as inclusion bodies and refolded by dilution. The refolded protein was purified to homogeneity, biochemical characterized and the solution structure was investigated using small-angle X-ray scattering (SAXS). The SAXS data revealed that IRp60 is monomeric in solution with a molecular shape characteristic of the immunoglobulin-like structures. A homology model of IRp60 was built and validated experimentally against the SAXS data.

Characterization of IQGAP1-containing complexes in NK-like cells: evidence for Rac 2 and RACK1 association during homotypic adhesion

IQGAP1 is a scaffolding protein that binds to a diverse array of signaling and structural molecules that are often associated with cell polarization and adhesion. Through interaction with its target proteins, IQGAP1 participates in multiple cellular functions, including Ca2+-calmodulin signaling, definition of cytoskeletal architecture, regulation of Cdc42 and Rac1 dependent cytoskeletal changes, and control of E-cadherin mediated intercellular adhesion. These analysis have been largely restricted to cells of epithelial and fibroblast origin. The present studies were initiated to examine the role of IQGAP1 in cellular interactions involving the lymphoid cells. A mass spectrometric based analysis of IQGAP1 containing complexes isolated from the human NK-like cell line, YTS, identified several known and new potential IQGAP1 interaction partners including receptor of activated C kinase 1 (RACK1) and the small GTPase, Rac2. Immunofluorescence analysis of YTS cells indicated that a minor component of IQGAP1 was localized at the cell membrane with the remainder diffusely distributed through out the cytoplasm. However, at sites of cellular contact, there was a marked accumulation of IQGAP1. Staining for RACK1 and Rac2 revealed that both of these proteins accumulated these contact sites. Antibody-based studies suggested that a subset of RACK1 was associated in an IQGAP1-containing complex, which prevented recognition of RACK1 by monoclonal antibody. These results suggest that RACK1, Rac2, and IQGAP1 are components of complexes involved in NK cell homotypic adhesion.

Hedistin: A novel antimicrobial peptide containing bromotryptophan constitutively expressed in the NK cells-like of the marine annelid, Nereis diversicolor

A novel antimicrobial peptide, named hedistin was identified from the coelomocytes of Nereis diversicolor. Hedistin shows no obvious similarities with other known peptides and constitutes the first antimicrobial peptide containing bromotryptophans demonstrated in annelids. cDNA and mass spectrometry analysis revealed that, upon bacteria challenge, this peptide is secreted following processing of a precursor containing a signal peptide and prosequences. Hedistin was shown to possess an activity against a large spectrum of bacteria including the methicillin resistant Staphylococcus aureus and Vibrio alginolyticus. The gene was demonstrated to be constitutively and exclusively expressed in circulating NK cells like known to play an important role in the immunity of the sand worm. These data contrast with those observed in another annelid, the leech, in which genes coding for antimicrobial peptides are upregulated in a specific tissue and peptides are rapidly released into the hemolymph after septic injury.

Long-term Haematopoietic Reconstitution and Survival without Interleukin-7 in a Murine Syngeneic Bone Marrow Transplantation Model

We created a syngeneic mouse bone marrow transplantation (BMT) model to examine the effect of endogenous interleukin-7 (IL-7) on long-term (>or=140 days) haematopoietic reconstitution and survival after BMT. Wild-type (WT) IL-7(+/+) and knockout (KO) IL-7(-/-) mice were lethally irradiated and transplanted with bone marrow. Survival is best (85.7%) in the group WT grafts transplanted into WT recipients (WT-->WT) with a trend towards poorer survival in the other groups (WT-->KO: 60%, KO-->WT: 50%, KO-->KO: 45.5%, differences statistically not significant). If the recipient is deficient for IL-7-producing cells, T- and B-cell reconstitution remain incomplete. If the graft lacks IL-7-producing cells there is a significant delay in T- and NK-cell reconstitution. Interestingly, in the absence of IL-7, T-cell reconstitution is neither delayed nor incomplete because of an expansion of TCRalphabeta(+)/CD4(-)/CD8(-) double negative T cells. Long-term survival and lymphocyte reconstitution after syngeneic BMT can occur despite the absence of IL-7.

Fulminant liver failure triggered by therapeutic antibody treatment in a mouse model

Monoclonal antibodies are finding ever increasing therapeutic applications. However, lethal liver damage has been reported following monoclonal antibody (mAb) treatment in combination with subtoxic doses of cytotoxic drugs. In this study, mice were intravenously injected with 200 microg/mouse of anti-CD8 (anti-Lyt-2.2), anti-CD4 (GK1.5) or anti-B220 (RA3-6B2) mAb. Subsequently, mice were administered 15 mg azoxymethane (AOM) per kg body weight by subcutaneous injection. Unexpectedly, all mice pretreated with mAb died within 72 h of a single injection of AOM. The injection of mAb-coated spleen cells accelerated the induction and the severity of liver disease. We found that mAb treatment activates Kupffer cells to produce inflammatory cytokines such as TNF-alpha and IL-12, and induces the expression of FasL on Kupffer and NKT cells. The concomitant upregulation of Fas on hepatocytes increases the susceptibility of the liver to apoptotic signals, and subsequent treatment with AOM causing mitochondrial injury synergistically induces lethal liver damage. Consistently, the lethal liver damage was abrogated in mice which were deficient for Kupffer cells, NKT cells or Fas-antigen. In conclusion, we have demonstrated a potential risk of lethal fulminant liver damage in the concomitant use of therapeutic antibodies and cytotoxic drugs. A possible side effect of antibody therapy is mediated through activation of the immune system, the very mechanism of action on which this treatment depends. In this context, the risk of combining therapeutic antibodies with other agents, particularly cytotoxic drugs, requires careful consideration.

Antitumor action of lymphokin-activated cells of patients with soft tissue sarcomas and melanomas in dependence on expression of MHC classes I and II antigenes

AIM

To study expression of major histocompatibility complex (MHC) classes and antigens and CD25, CD71, Ki-67, CD54, CD56, CD11b, PCNA on lymphocytes and tumor cells and antitumor action of lymphocytes activated with IL-2.

MATERIALS AND METHODS

Tumor explants (soft tissue sarcoma, n = 20, melanoma, n = 25) were co-cultivated in diffusion chambers with autologous lymphocytes; antitumor action was evaluated by morphologic patterns of explant's growth. Expression of CD25, CD71, Ki-67, CD54, CD56, CD11b, PCNA was evaluated by the method of indirect fluorescence using respective monoclonal antibodies.

RESULTS

The highest antitumor action of lymphocytes toward soft tissue sarcoma and melanoma cells is observed if tumor cells are expressing MHC class I antigens. In the cases of soft tissue sarcoma no correlation between the level of antitumor activity of lymphocytes and expression of CD25, CD71, Ki-67, CD54, CD56, CD11b, PCNA has been found, whilst in the case of melanoma it is associated with the high level of CD11b expression.

CONCLUSION

There is a direct correlation between sensitivity of soft tissue sarcoma and melanoma cells to action of lymphokin-activated killer cells and the level of MHC class I antigens.

Increased stress-induced inflammatory responses in male patients with major depression and increased early life stress

OBJECTIVE

The authors sought to determine innate immune system activation following psychosocial stress in patients with major depression and increased early life stress.

METHOD

Plasma interleukin (IL)-6, lymphocyte subsets, and DNA binding of nuclear factor (NF)-kB in peripheral blood mononuclear cells were compared in medically healthy male subjects with current major depression and increased early life stress (N=14) versus nondepressed male comparison subjects (N=14) before and after completion of the Trier Social Stress Test.

RESULTS

Trier Social Stress Test-induced increases in IL-6 and NF-kappaB DNA-binding were greater in major depression patients with increased early life stress and independently correlated with depression severity, but not early life stress. Natural killer (NK) cell percentages also increased following stress. However, there were no differences between groups and no correlation between NK cell percentage and stress-induced NF-kappaB DNA-binding or IL-6.

CONCLUSIONS

Male major depression patients with increased early life stress exhibit enhanced inflammatory responsiveness to psychosocial stress, providing preliminary indication of a link between major depression, early life stress and adverse health outcomes in diseases associated with inflammation.

DNAse treatment following thawing of Cryopreserved PBMC is a procedure suitable for lymphocyte functional studies

Testing freshly isolated PBMC is not practical for immune monitoring analysis in large clinical trials or natural history studies. Thus, cryopreserved PBMC represent a more practical alternative. However, cell clumping is a common problem following thawing of PBMC isolated from blood that was previously transported and stored. Cell clumping leads to loss of cells, and could affect cell function and/or phenotype. The development and validation of procedures that prevent cell clumping and preserve cell function and surface marker expression levels are necessary to allow evaluation of immune function and phenotype in cryopreserved samples from clinical studies. The incorporation of a DNAse treatment step in the standard thawing procedure efficiently avoided clump formation, and did not result in detectable changes in cell viability, expression of standard leukocyte surface markers or two key parameters of immune function, proliferation and cytokine induction in response to a variety of common stimuli. Therefore, this procedure seems suitable for standard immunologic assays.

Nine fluorescence parameter analysis on a four-color fluorescence activated flow cytometer

BACKGROUND

In many cases a frequent monitoring of blood is important, e.g. during an infection. Often the availability of blood is the limiting factor.

METHODS

50 microl blood were stained and analyzed using a standard four-color cytometer. Percentages of leukocytes were calculated by FlowJo software.

RESULTS

Our protocol allows the differentiation of B cells, T cells, NK cells, neutrophils, and monocytes/macrophages in small volumes of blood.

CONCLUSIONS

Using nine fluorochrome-labeled antibodies and a specific gating strategy we were able to differentiate the main immune cells in minute amounts using one staining step.

Weight-dependent changes of immune system in adipose tissue: importance of leptin

Ancestral lymphoid cells reside in adipose tissues, and their numbers are highly altered in obesity. Leptin, production of which is correlated to fat mass, is strongly involved in the relationships between adipose tissues and immune system. We investigated in epididymal (EPI) and inguinal (ING) fat pads to determine whether 1) lymphocyte phenotypes were correlated to the tissue weight and 2) leptin was involved in such relationships. Immunohistological analyses revealed a tight relationship between the T and NK lymphocytes of the stromal vascular fraction and adipocytes. We identified a significant negative and positive correlation between EPI weight and the percentage of NK and total T cells respectively by cytofluorometric analyses. The NK and ancestral gammadelta T cell contents were directly dependent of leptin since they increased significantly in high-fat (HF) diet mice but not in leptin-deficient (ob/ob) mice as compared to control. By contrast, the alphabeta T cell content seemed independent of leptin because their percentages increased significantly with the EPI weight whatever the type of mice (control, HF, ob/ob). The present study suggests that adipose tissues present, according to their localization, different immunological mechanisms that might be involved in the regulation of adipose cells functions and proliferations.

Human NK cell IFN-gamma production is regulated by endogenous TGF-beta

NK cells are an important component of innate immunity, and they can promote CTL and Th1 cell development and macrophage activation via cytokines. TGF-beta is believed to be an important immunoregulatory molecule, and for this reason several TGF-beta inhibitors are currently in clinical development. However, the modulation of specific innate immune responses by endogenous human TGF-beta remains unclear. In this study, we demonstrate that blocking the action of endogenous TGF-beta resulted in an increase in both the percentage of responding NK cells and the amount of IFN-gamma produced by human NK cells when stimulated by monokines and TLR agonists. Blocking endogenous TGF-beta resulted in significant NK cell IFN-gamma production under suboptimal stimulation conditions. Our findings also suggest that TGF-beta associated with other blood cells may be involved in limiting NK cell activation. Thus, inhibiting endogenous TGF-beta provides a means to shift NK cell activation and promote cellular immunity.

Modulation of natural killer (NK) receptors on NK (CD3-/CD56+), T (CD3+/CD56-) and NKT-like (CD3+/CD56+) cells after heart transplantation

BACKGROUND

After undergoing heart transplantation and the subsequent compulsive immunosuppressive treatments, patients are at risk of rejection episodes, infectious complications or cancer development. Thus, it is probable that the various subsets of peripheral cytotoxic lymphocytes are modulated in such patients. This area of study can now be investigated by examining the numerous recently described natural killer (NK)-cell-related surface receptors.

METHODS

A prospective cohort of 60 heart transplant recipients and 60 controls was studied. The partitioning of lymphocyte subsets, especially NK (CD3-/CD56+), T (CD3+/CD56-) and NKT-like (CD3+/CD56+) cells, was compared in both groups using multi-parametric flow cytometry. Moreover, expression of a series of seven NK-related receptors was compared on the three subsets defined by CD56 expression.

RESULTS

A significant increase in NK-cell levels was observed in transplanted patients, as compared with controls, whereas T and NKT-like cells were in similar proportions in both groups. Two NK-related receptors showed significantly different levels of expression in heart transplant recipients: the cytotoxic effector, CD244, which was in a significantly increased proportion on T and NKT-like cells; and the activating receptor, CD161, which was expressed significantly less on NK and NKT-like cells, but more on T cells.

CONCLUSIONS

These findings indicate that cytotoxic NK-related cells, increased in proportion, also display increased levels of activity-associated markers in heart transplant recipients. Viral infection or the immunosuppressive regimen could be responsible for the modulation of regulatory receptors on NK and NKT-like cells in heart transplant recipients.

Immune surveillance of the human central nervous system (CNS): Different migration pathways of immune cells through theblood–brain barrier and blood–cerebrospinal fluid barrier in healthy persons

BACKGROUND

Since for immune surveillance, only lymphocytes in the activated state are able to enter normal human central nervous system (CNS), available data are briefly reviewed to reveal lymphocyte transfer through blood-brain barrier (bbb) and blood-cerebrospinal fluid barrier (bCSFb).

METHODS

With immuno-histochemical and -cytochemical methods, bbb was studied on brain microvessels and bCSFb on choroid plexus epithelium and microvessels. Lymphocyte transfer capacity on the barriers was determined with blood/CSF cell ratios revealed by quantified multicolour flow-cytometry of CSF and blood sample pairs.

RESULTS

Four paths attenuated the restricted transfer of lymphocyte and NK cell subsets (none for B cells) through bbb and bCSFb, preferring memory cells in normal human brain, using different cell adhesion molecules (CAM). CAM pattern changed in choroid plexus where indication of lymphocyte recirculating from CSF into blood may exist in animal brains.

CONCLUSIONS

Since efficiency of migration of blood-borne lymphocytes into CSF across bbb or bCSFb of normal human brain is not fully revealed, further data are needed to understand the transfer of immune cells across the barriers in health and disease.

An optimized whole blood method for flow cytometric measurement of ZAP-70 protein expression in chronic lymphocytic leukemia

BACKGROUND

ZAP-70 protein expression has been proposed as a marker for immunoglobulin heavy chain mutational status, which some studies have correlated with disease course in B-cell chronic lymphocytic leukemia (CLL). Studies published to date measuring levels of expression of ZAP-70 intracellular protein using flow cytometry have demonstrated poor performance, as defined by the difference in signal in known positive and negative lymphocyte populations.

METHODS

A recently published method (Chow S, Hedley DW, Grom P, Magari R, Jacobberger JW, Shankey TV, Cytometry A 2005;67:4-17) to measure intracellular phospho-epitopes was optimized using a design of experiments (DOE) approach to provide the best separation of ZAP-70 expression in positive T- or NK-cells as compared to negative B-cells in peripheral blood samples. A number of commercially available anti-ZAP-70 antibody-conjugates were screened using this methodology, and the antibody-conjugate showing the best performance was chosen to develop a four-color, five antibody assays to measure ZAP-70 levels in whole blood specimens.

RESULTS

Using the optimized fixation and permeabilization method, improvement in assay performance (signal-to-noise, S/N) was seen in most of the antibodies tested. The custom SBZAP conjugate gave the best S/N when used in conjunction with this optimized fixation /permeabilization method. In conjunction with carefully standardized instrument set-up protocols, we obtained both intra- and interlaboratory reproducibility in the analysis of ZAP-70 expression in whole blood samples from normal and CLL patients.

CONCLUSIONS

The development of a sensitive, specific and highly reproducible ZAP-70 assay represents only the first essential step for any clinical assay. The universal implementation of a validated data analysis method and the establishment of methodology-based cutoff points for clinical outcomes must next be established before ZAP-70 protein analysis can be routinely implemented in the clinical laboratory.

Single-cell analysis by intracellular immuno-reaction and capillary electrophoresis with laser-induced fluorescence detection

A novel method for single-cell analysis was developed by combining electroporation for intracellular immuno-reaction and capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection. Human interferon-gamma (IFN-gamma) in natural killer (NK) cells was chosen as the test antigen. Two forms of IFN-gamma in single cells could be well separated and detected with a limit of detection of zeptomole. In this assay, the anti-IFN-gamma monoclonal antibody labeled with fluorescein isothiocyanate (Ab*) was introduced into NK cells by electrophoration for intracellular immuno-reaction. After completion of the intracellular immuno-reaction, the NK cells were chemically pre-perforated with digitonin to lyse easily. Then, one NK cell containing the complexes of IFN-gamma isoantigens with Ab* was electrokinetically injected into the capillary. The cell adsorbed on the tip of capillary was lysed by ultrasonication. Finally, the complexes of the different forms of IFN-gamma in the cell were separated and detected by CE-LIF detection.

Histone hyperacetylated domains across the Ifng gene region in natural killer cells and T cells

Local histone acetylation of promoters precedes transcription of many genes. Extended histone hyperacetylation at great distances from coding regions of genes also occurs during active transcription of gene families or individual genes and may reflect developmental processes that mark genes destined for cell-specific transcription, nuclear signaling processes that are required for active transcription, or both. To distinguish between these, we compared long-range histone acetylation patterns across the Ifng gene region in natural killer (NK) cells and T cells that were or were not actively transcribing the Ifng gene. In T cells, long-range histone acetylation depended on stimulation that drives both T helper (Th) 1 differentiation and active transcription, and it depended completely or partially on the presence of Stat4 or T-bet, respectively, two transcription factors that are required for Th1 lineage commitment. In contrast, in the absence of stimulation and active transcription, similar histone hyperacetylated domains were found in NK cells. Additional proximal domains were hyperacetylated after stimulation of transcription. We hypothesize that formation of extended histone hyperacetylated domains across the Ifng gene region represents a developmental mechanism that marks this gene for cell- or stimulus-specific transcription.

Filter Buffy Coats (FBC): a source of peripheral blood leukocytes recovered from leukocyte depletion filters

In compliance with federal regulations, blood banks routinely use leukocyte depletion filters to eliminate contaminating leukocytes from blood products such as red blood cell and platelet concentrates. We developed and optimized conditions to elute leukocytes adsorbed to these filters; resulting in leukocyte suspensions which we termed Filter Buffy Coats (FBCs). These Filter Buffy Coats can replace standard buffy coats for various research applications. After optimizing both the filter elution medium as well as elution protocols, we compared commonly used leukocyte depletion filters from four different manufacturers. Relative fractions as well as total recoveries of leukocyte subsets, such as lymphocytes, monocytes and granulocytes, found in Filter Buffy Coats were identified and compared among the filters as well as to standard buffy coats and whole blood. Flow cytometric analysis of Filter Buffy Coats confirmed the presence of T- and B-lymphocytes, NK cells and monocytes. Furthermore, a significant quantity of CD34(+) hematopoietic stem or progenitor cells (HSC/HPC) was detected in Filter Buffy Coats prepared from different filters, thus making FBCs a valuable source for research on HSC/HPC. Colony assays revealed that most of these CD34(+) cells are functional. Using immunomagnetic cell sorting (MACS), we isolated a variety of leukocyte populations from FBC mononuclear cells (Filter-PBMCs) including T lymphocytes (CD4(+), CD8(+), CD3(+)), B lymphocytes (CD19(+)), NK cells (CD56(+)), HSC/HPC (CD34(+), CD133(+)) or dendritic cells (BDCA-4(+)). Functional properties of Filter-PBMCs, as well as of some of these isolated leukocyte populations, were confirmed using standard assays. In summary, Filter Buffy Coats are a valuable and convenient source of different peripheral leukocyte populations and can replace standard buffy coat preparations for research applications.

A high-efficiency system of natural killer cell cloning

The culture of human natural killer (NK) cell clones has traditionally been a long, laborious process with an efficiency of only 1-2%. Recently, a stem cell growth medium (SCGM) has been described to expand preferentially polyclonal NK cells from peripheral blood. We have tested SCGM in a single cell sorting system and shown a 4-5 fold increase in the number of proliferating NK clones compared to standard RPMI media. The cloning efficiency was further enhanced by the provision of irradiated feeder cells derived from multiple donors combined with the addition of the anti-CD3 antibody, OKT3. The combination of SCGM, single cell sorting and these multiple optimisations enhanced NK cloning efficiency by more than tenfold to greater than 20% for short-term cultures when deriving 10(5) cells and as high as 10% for longer term cultures when deriving more than 2 x 10(6) cells. This novel system thus facilitates the generation of NK clones and allows larger scale studies of NK function that were beyond the scope of previous methodology.

The characteristics of human NKT cells in lung cancer--CD1d independent cytotoxicity against lung cancer cells by NKT cells and decreased human NKT cell response in lung cancer patients

The activation of human Valpha24+Vbeta11+natural killer T cells (NKT) cells (Valpha24 NKT cells) induces effective antitumor responses with secondary immune effects through activation of conventional T cells and natural killer cells. In this study, we attempted to analyze the characteristics of human NKT cells in lung cancer patients. Valpha24 NKT cells stimulated with alpha-GalCer from healthy volunteers exhibited direct cytotoxic activity against two (RERF-LC-OK and PC-3) of seven human lung cancer cell lines studied. Cytotoxicity by Valpha24 NKT cells against human lung cancer cells was dependent on the perforin pathway and independent of Fas/FasL pathway. Intracellular adhesion molecule (ICAM)-1 expression on tumor cells was clearly associated with the cytotoxicity of Valpha24 NKT cells. On the other hand, the proportion of Valpha24 NKT cells in the patients with lung cancer was lower than that in the healthy volunteers. Furthermore, the proliferative response of Valpha24 NKT cells to alpha-GalCer was significantly lower in the peripheral blood mononuclear cells in the patients with lung cancer. Addition of granulocyte colony-stimulating factor moderately restored the low proliferative response of Valpha24 NKT cells in the patients with lung cancer, however the percentage by which the response was restored in these patients was still lower than the natural response in healthy volunteers. These results suggest that Valpha24 NKT cells may play a pivotal role or the antitumor response in lung cancer.

Proteome characterization of human NK-92 cells identifies novel IFN-alpha and IL-15 target genes

Natural killer (NK) cells are important components of innate immune defense. NK cells kill virus-infected cells and secrete cytokines that are involved in activation of other immune cells. Macrophage-derived cytokines interferon-alpha (IFN-alpha) and interleukin-15 (IL-15) are in turn important activators of NK cells, but the receptors and intracellular pathways that are involved in NK cell functions are still incompletely known. Here we have used expression proteomics to find new IFN-alpha and IL-15 regulated proteins in human NK-92 cells, which have the characteristics of activated NK cells. Cells were stimulated with cytokines for 20 h, lysed, and soluble proteins were separated by two-dimensional electrophoresis, and differentially expressed protein spots were identified with mass spectrometry and database searches. A total of 57 protein spots were found to be reproducibly differentially expressed between control and cytokine stimulated gel pairs, 26 spots being more than 2-fold upregulated and 3 spots being at least 2-fold downregulated. The rest 28 spots showed minor, less than 2-fold changes in their expression levels after quantification. From the differentially expressed protein spots we identified 47 different proteins, most of which are new IFN-alpha and IL-15 target proteins. Interestingly, we show that e.g., adenylate kinase 2 is highly upregulated by IFN-alpha and IL-15 stimulation in NK-92 cells. The expression of selected genes with high expression level differences after cytokine stimulation were further studied at mRNA level. Northern blot analysis showed that the genes studied were induced by IFN-alpha, IL-15, and IL-2 already at 3 h time point, suggesting that they are primary target genes of these cytokines.

Identification of NKG2A and NKp80 as specific natural killer cell markers in rhesus and pigtailed monkeys

Investigations of natural killer (NK) cells in simian models of disease have been hampered by a lack of appropriate phenotypic markers and by an inadequate understanding of the regulation of NK cell activities. In the present study, a panel of monoclonal antibodies (mAbs) specific for various human NK receptors was screened for cross-reactivity with NK cells from rhesus macaques and pigtailed macaques. Flow cytometric analyses using anti-human NKG2A and anti-human NKp80 mAbs individually, and particularly in combination with anti-CD16 mAb, allowed for the identification of the entire NK cell population in both species. NK cells in monkeys were generally identified by negative selection of peripheral blood mononuclear cells (PBMCs) for the absence of T-cell, B-cell, and monocyte markers. mAb-mediated ligation of NKp80 induced NK cell cytotoxicity, while in the case of NKG2A it displayed a clear capability to inhibit the lysis of target cells by NK cells from macaques, as well as from humans. This new phenotypic and functional characterization of NKG2A and NKp80 in rhesus and pigtailed macaque NK cells provides a new approach in the analysis of their innate immune system.

Ly49 and CD94/NKG2 receptor acquisition by NK cells does not require lymphotoxin-β receptor expression

A crucial step in murine natural killer (NK) cell development, mediated by bone marrow stromal cells, is the induction of Ly49 and CD94/NKG2 receptor expression. The signals that regulate Ly49 receptor expression are still largely undetermined. It has been shown that interaction between lymphotoxin α1β2 (LTα1β2) and LTβ receptor (LTβR), expressed on lymphoid progenitor cells and nonlymphoid bone marrow stromal cells, respectively, is important for both quantitative and functional NK cell development. Therefore, we have investigated the role of LT-LTβR–mediated signaling in Ly49 and CD94/NKG2 receptor acquisition. We show that the NK receptor repertoire of LTβR–/– mice can only be partially analyzed because of the residual 129/Ola mouse genetic background, due to a physical linkage of the LTβR locus and the loci encoding the Ly49 and CD94/NKG2 receptors. Therefore, we transferred wild-type B6 lymphoid-committed progenitor cells into LTβR–/– mice, which differentiated into NK cells with a normal NK cell receptor repertoire. Also, administration of LTβR-immunoglobulin (Ig), which acts as a soluble receptor for LTα1β2, resulted in reduced NK cell percentages but did not influence the Ly49 and CD94/NKG2 receptor acquisition on remaining NK cells. These results indicate that LTβR-mediated signals are not required for Ly49 and CD94/NKG2 receptor acquisition.

Structure and function of a potent agonist for the semi-invariant natural killer T cell receptor

Natural killer T cells express a conserved, semi-invariant alphabeta T cell receptor that has specificity for self glycosphingolipids and microbial cell wall alpha-glycuronosylceramide antigens presented by CD1d molecules. Here we report the crystal structure of CD1d in complex with a short-chain synthetic variant of alpha-galactosylceramide at a resolution of 2.2 A. This structure elucidates the basis for the high specificity of these microbial ligands and explains the restriction of the alpha-linkage as a unique pathogen-specific pattern-recognition motif. Comparison of the binding of altered lipid ligands to CD1d and T cell receptors suggested that the differential T helper type 1-like and T helper type 2-like properties of natural killer T cells may originate largely from differences in their 'loading' in different cell types and hence in their tissue distribution in vivo.

Significance of chemokine receptor expression in aggressive NK cell leukemia

Natural killer (NK) cell-type lymphoproliferative diseases of granular lymphocytes can be subdivided into aggressive NK cell leukemia (ANKL) and chronic NK cell lymphocytosis (CNKL). One reason for the poor outcome in ANKL is leukemic infiltration into multiple organs. The mechanisms of cell trafficking associated with the chemokine system have been investigated in NK cells. To clarify the mechanism of systemic migration of leukemic NK cells, we enrolled nine ANKL and six CNKL cases, and analyzed the expression profiles and functions of chemokine receptors by flowcytometry and chemotaxis assay. CXCR1 was detected on NK cells in all groups, and CCR5 was positive in all ANKL cells. Proliferating NK cells were simultaneously positive for CXCR1 and CCR5 in all ANKL patients examined, and NK cells with this phenotype did not expand in CNKL patients or healthy donors. ANKL cells showed enhanced chemotaxis toward the ligands of these receptors. These results indicated that the chemokine system might play an important role in the pathophysiology of ANKL and that chemokine receptor profiling might be a novel tool for discriminating ANKL cells from benign NK cells.

Two structurally related rat Ly49 receptors with opposing functions (Ly49 stimulatory receptor 5 and Ly49 inhibitory receptor 5) recognize nonclassical MHC class Ib-encoded target ligands

The Ly49 family of lectin-like receptors in rodents includes both stimulatory and inhibitory members. Although NK alloreactivity in mice is regulated primarily by inhibitory Ly49 receptors, in rats activating Ly49 receptors are equally important. Previous studies have suggested that activating rat Ly49 receptors are triggered by polymorphic ligands encoded within the nonclassical class Ib region of the rat MHC, RT1-CE/N/M, while inhibitory Ly49 receptors bind to widely expressed classical class Ia molecules encoded from the RT1-A region. To further investigate rat Ly49-mediated regulation of NK alloreactivity, we report in this study the identification and characterization of two novel paired Ly49 receptors that we have termed Ly49 inhibitory receptor 5 (Ly49i5) and Ly49 stimulatory receptor 5 (Ly49s5). Using a new mAb (mAb Fly5), we showed that Ly49i5 is an inhibitory receptor that recognizes ligands encoded within the class Ib region of the u and l haplotypes, while the structurally related Ly49s5 is an activating receptor that recognizes class Ib ligands of the u haplotype. Ly49s5 is functionally expressed in the high NK-alloresponder PVG strain, but not in the low alloresponder BN strain, in which it is a pseudogene. Ly49s5 is hence not responsible for the striking anti-u NK alloresponse previously described in BN rats (haplotype n), which results from repeated alloimmunizations with u haplotype cells. The present studies support the notion of a complex regulation of rat NK alloreactivity by activating and inhibitory Ly49 members, which may be highly homologous in the extracellular region and bind similar class Ib-encoded target ligands.

CXCR6 within T-helper (Th) and T-cytotoxic (Tc) type 1 lymphocytes in Graves' disease (GD)

OBJECTIVE

In Graves' disease (GD), stimulating anti-TSH receptor antibodies are responsible for hyperthyroidism. T-helper 2 (Th2) cells were expected to be involved in the underlying immune mechanism, although this is still controversial. The aim of this study was to examine the expression of CXCR6, a chemokine receptor that marks functionally specialized T-cells within the Th1 and T-cytotoxic 1 (Tc1) cell pool, to gain new insights into the running immune processes.

METHODS

CXCR6 expression was examined on peripheral blood lymphocytes (PBLs) and thyroid-derived lymphocytes (TLs) of GD patients in flow cytometry. CXCR6 cDNA was quantified in thyroid tissues affected by GD (n = 16), Hashimoto's thyroiditis (HT; n = 2) and thyroid autonomy (TA; n = 11) using real-time reverse transcriptase PCR.

RESULTS

The percentages of peripheral CXCR6(+) PBLs did not differ between GD and normal subjects. CXCR6 was expressed by small subsets of circulating T-cells and natural killer (NK) cells. CXCR6(+) cells were enriched in thyroid-derived T-cells compared with peripheral CD4(+) and CD8(+) T-cells in GD. The increase was evident within the Th1 (CD4(+) interferon-gamma(+) (IFN-gamma(+))) and Tc1 (CD8(+)IFN-gamma(+)) subpopulation and CD8(+) granzyme A(+) T-cells (cytotoxic effector type). Thyroid-derived fibro-blasts and thyrocytes were CXCR6(-). There was no significant difference between the CXCR6 mRNA levels in GD compared with HT and normal TA tissues. The lowest CXCR6 mRNA levels were obtained from thyroid nodules from TA patients and GD patients with low thyroid peroxidase autoantibody levels.

CONCLUSIONS

CXCR6 was overexpressed in Th1 and Tc1 TLs compared with PBLs in GD. CXCR6 could be a marker for lymphocytes that have migrated into the thyroid and assist in the thyroid, independently of the bias of the underlying disease.

TRAIL identifies immature natural killer cells in newborn mice and adult mouse liver

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a key effector molecule expressed by natural killer (NK) cells and has been shown to prevent tumor initiation, growth, and metastasis. Here we demonstrate that TRAIL is the dominant cytotoxic effector molecule expressed by NK cells in fetal mice. On birth and with age, NK cells develop full functional capacity, including the ability to secrete interferon gamma (IFN-gamma) and interleukin 13 (IL-13) and mediate perforin- and Fas ligand-mediated cytotoxicity. However, interestingly, a phenotypically immature TRAIL+ NK cell subpopulation is retained in the liver of adult mice, and its retention is dependent on IFN-gamma but not dependent on host IL-12, IL-18, or endogenous host pathogens. Adoptive transfer of either adult liver or neonatal TRAIL+ NK cells resulted in the appearance of TRAIL- NK cells with a mature phenotype, suggesting that these TRAIL+ NK cells were indeed a precursor. Although inducers of IFN-gamma stimulated TRAIL expression on mature NK cells, our data indicated that constitutive TRAIL expression was a hallmark of immature cytotoxic NK cells. This study is the first to describe the concomitant maturation of NK cell effector function with surface phenotype in vivo and implies an important defense role for NK cell TRAIL in the developing immune system.

Structure of the Ly49 family of natural killer (NK) cell receptors and their interaction with MHC class I molecules

Natural killer (NK) cells are an essential component of the innate immunity toward tumors and virally infected cells. The function of NK cells is regulated by a precise balance between inhibitory and activating signals. These signals are mediated by NK cell receptors that bind either classical MHC class I molecules or their structural relatives such as MICA, ULBP, RAE-1, and H-60. Two separate families of NK cell receptors have been identified: the immunoglobulin-like family (KIR, LIR) and C-type lectin-like family (Ly49, NKG2D, and CD94/NKG2). Here we summarize the structure of Ly49 C-type lectin-like proteins hitherto solved (Ly49A, Ly49C and Ly49I) and their interaction with MHC class I molecules as determined by the co-crystal structure of Ly49A/H-2Dd and Ly49C/H-2Kb.

Structural and functional aspects of the Ly49 natural killer cell receptors

Natural killer cells are part of the first line of innate immune defence against virus-infected cells and cancer cells in the vertebrate immune system. They are called 'natural' killers because, unlike cytotoxic T cells, they do not require a previous challenge and preactivation to become active. The Ly49 NK receptors are type II transmembrane glycoproteins, structurally characterized as disulphide-linked homodimers. They share extensive homology with C-type lectins, and they are encoded by a multigene family that in mice maps on chromosome 6. A fine balance between inhibitory and activating signals regulates the function of NK cells. Inhibitory Ly49 molecules bind primarily MHC class I ligands, whereas the ligands for activating Ly49 molecules may include MHC class I, but also interestingly MHC class I-like molecules expressed by viruses, as is the case for Ly49H, which binds the m157 gene product of murine cytomegalovirus. In this study, we review the function and X-ray crystal structure of the Ly49 NK cell receptors hitherto determined (Ly49A, Ly49C and Ly49I), and the structural features of the Ly49/MHC class I interaction as revealed by the X-ray crystal structures of Ly49A/H-2Dd and the recently determined Ly49C/H-2Kb.

HLA-G up-regulates ILT2, ILT3, ILT4, and KIR2DL4 in antigen presenting cells, NK cells, and T cells

The nonclassical HLA class I antigen HLA-G is an inhibitory molecule involved in immune tolerance and immune escape. HLA-G exerts its inhibitory functions via interaction with inhibitory receptors ILT2, ILT4, and KIR2DL4, differentially expressed by NK, T, and antigen-presenting cells. Cells expressing HLA-G and cells expressing its receptors are often found in the vicinity of each other, but the mechanisms responsible for this colocalization are still unknown. We report that ILT2, ILT3, ILT4, and KIR2DL4 expression is up-regulated by HLA-G in antigen-presenting cells, NK cells, and T cells. Because this up-regulation seems not to require antigenic costimulation, it might precede an immune response. Functionally, up-regulation of inhibitory receptors in immune cells before stimulation might increase their activation thresholds and participate in immune escape mechanisms.

A novel four-colour flow cytometric assay to determine natural killer cell or T-cell-mediated cellular cytotoxicity against leukaemic cells in peripheral or bone marrow specimens containing greater than 20% of normal cells

To be able to determine the cytotoxic activity of NK cells or T cells against leukaemic cells in patient samples containing >20% of normal peripheral blood cells, we have developed a four-colour flow cytometric cytotoxicity assay. The assay is based on differential immunostaining of both leukaemic cells and effector cells in combination with propidium iodide (PI). The cytometer is set for measuring the fluorescence of the monoclonal antibody (mAb) bound fluorochromes, with moderate overcompensation of the third and fourth fluorescence signals. PI-positive events were excluded from analysis by their characteristic uncompensated signal on these two detectors. Thus, all four fluorescence ranges can be used for detection of mAb-derived signals and this allows discrimination between various populations contained in effector and target cell samples. The cytotoxic activity in our assay is calculated by the absolute loss of vital leukaemic cells. For this purpose, fluorescent beads are included as an internal standard. When calculating the effector concentrations after coculture, characteristic changes can be seen which yield additional information about the presence of cytotoxic activity and the active effector cell subset. With this assay, we present a versatile tool that combines minimum cell manipulation before coculture with maximum information from a sample. The assay is suitable for the analysis of complex samples with regard to different cell subsets, their decrease or increase, and conjugate formation.

Mass spectrometric analysis of the glycosphingolipid-enriched microdomains of rat natural killer cells

Glycosphingolipid-enriched microdomains (GEM) are membrane entities that concentrate glycosylphosphatiolylinositol(GPI)-anchored, acylated and membrane proteins important for immune receptor signaling. Using rat leukemic cell line RNK-16 we have initiated proteomic studies of microdomains in natural killer (NK) cells. Isolated plasma membranes were treated with Brij 58, or Nonidet-P40, or sodium carbonate. Extracts were separated by sucrose density gradient centrifugation into very light membrane, medium light membrane and heavy fractions, and a complete protein profile was analyzed by tandem mass spectrometry. Up to 250 proteins were unambiguously identified in each analyzed fraction. The first study of the proteome of NK cell GEM revealed several new aspects including identification of molecules not expected to be expressed in rat NK cells (e.g., NAP-22) or associated with GEM (e.g., NKR-P1, CD45, CD2). Moreover, it provided clear data consolidating controversial views concerning the occurrence of major histcompatibility complex glycoproteins and RT6.1/CD73/CD38 complex in NK cells. Our results also identified a large number of receptors as candidates for future functional studies.

Quantitative and Qualitative Differences in Proatherogenic NKT Cells in Apolipoprotein E–Deficient Mice

Background— Atherosclerosis is a disease marked by lipid accumulation and inflammation. Recently, atherosclerosis has gained recognition as an autoimmune-type syndrome characterized by increased activation of the innate and acquired immune systems. Natural killer T (NKT) cells have characteristics of both conventional T cells and NK cells and recognize glycolipid antigens presented in association with CD1d molecules on antigen-presenting cells. The capacity of NKT cells to respond to lipid antigens and modulate innate and acquired immunity suggests that they may play a role in atherogenesis.

Methods and Results— We examined the role of NKT cells in atherogenesis and how the atherosclerotic environment affects the NKT cell population itself. The data show that CD1d-deficiency in male apolipoprotein E–deficient (apoE 0 ) mice results in reduction in atherosclerosis, and treatment of apoE 0 mice with α-galactosylceramide, a potent and specific NKT cell activator, results in a 2-fold increase in atherosclerosis. Interestingly, we demonstrate that α-galactosylceramide–induced interferon-γ responses and numbers of NKT cells in apoE 0 mice show age-dependent qualitative and quantitative differences as compared with age-matched wild-type mice.

Conclusions— Collectively, these findings reveal that hyperlipidemia and atherosclerosis have significant effects on NKT cell responses and that these cells are proatherogenic.

Evidence for immune defects in breast and lung cancer patients

Immunosuppression is often identified in cancer patients. The aim of this study was to evaluate several immune parameters for patients with breast and lung cancer. Immunophenotyping analysis showed that the cancer patients investigated had significantly lower absolute numbers of peripheral blood lymphocytes than controls. The immunosuppression was more evident for the breast cancer subgroup. The most severe immune defect noticed was the marked impairment of IFN-gamma secretion. A shift toward the Th2 phenotype as revealed by assessment of intracellular level of IFN-gamma and IL-4 was also noticed. The secretion of proinflammatory cytokines IL-1beta and TNF-alpha in whole blood cultures was not impaired. Although the proportion of activated cells was slightly lower than in the control group, our results showed that both peripheral T lymphocytes and NK cells of cancer patients could be induced to express early activation marker CD69 after ex vivo mitogen stimulation. In conclusion, our study revealed several immune defects in cancer patients. This suggests that an appropriate immunotherapeutical approach might be used to restore compromised immune functions with beneficial effects on both antitumor and general immunity.

The proportion of follicular fluid CD16+CD56DIM NK cells is increased in IVF patients with idiopathic infertility

One-fifth of all in-vitro fertilization (IVF) patients suffer from idiopathic infertility. A low fertilization rate is one of the most characteristic features of IVF in this group, probably caused by oocyte dysfunction. We speculate that an altered lymphocyte profile in follicular fluid (FF) may affect oocyte function and thus play a role in idiopathic infertility. Therefore, we compared levels of lymphocyte populations present in FF of 11 patients with idiopathic infertility (study group) with 29 patients in the control group, i.e. severe male factor infertility (n=17) or tubal factor infertility (n=12). Triple color flow cytometry was used to discriminate between T cells and NK cell subpopulations. In the idiopathic infertility group, a shift from T to NK cells was observed in FF as compared to the control group, caused mainly by a significant higher level of NK cells--20.3 and 13.6% (P<0.05), respectively. This high level of NK cells was due to a rise of the CD16+CD56dim NK cell subset. In peripheral blood, the NK cell levels showed a similar although not significant trend (P=0.08). As the CD16+CD56dim NK cell subpopulation is known for its cytotoxic properties, this subpopulation may negatively affect folliculogenesis and oocyte maturation, reflected by a diminished fertilization rate in the idiopathic infertility group. An altered lymphocyte profile in FF could therefore influence fertility in these patients.

Natural killer cell dysfunction is a distinguishing feature of systemic onset juvenile rheumatoid arthritis and macrophage activation syndrome

Macrophage activation syndrome (MAS) has been reported in association with many rheumatic diseases, most commonly in systemic juvenile rheumatoid arthritis (sJRA). Clinically, MAS is similar to hemophagocytic lymphohistiocytosis (HLH), a genetic disorder with absent or depressed natural killer (NK) function. We have previously reported that, as in HLH, patients with MAS have profoundly decreased NK activity, suggesting that this abnormality might be relevant to the pathogenesis of the syndrome. Here we examined the extent of NK dysfunction across the spectrum of diseases that comprise juvenile rheumatoid arthritis (JRA). Peripheral blood mononuclear cells (PBMC) were collected from patients with pauciarticular (n = 4), polyarticular (n = 16), and systemic (n = 20) forms of JRA. NK cytolytic activity was measured after co-incubation of PBMC with the NK-sensitive K562 cell line. NK cells (CD56⁺/T cell receptor [TCR]-αβ^-), NK T cells (CD56⁺/TCR-αβ⁺), and CD8⁺ T cells were also assessed for perforin and granzyme B expression by flow cytometry. Overall, NK cytolytic activity was significantly lower in patients with sJRA than in other JRA patients and controls. In a subgroup of patients with predominantly sJRA, NK cell activity was profoundly decreased: in 10 of 20 patients with sJRA and in only 1 of 20 patients with other JRA, levels of NK activity were below two standard deviations of pediatric controls (P = 0.002). Some decrease in perforin expression in NK cells and cytotoxic T lymphocytes was seen in patients within each of the JRA groups with no statistically significant differences. There was a profound decrease in the proportion of circulating CD56^bright NK cells in three sJRA patients, a pattern similar to that previously observed in MAS and HLH. In conclusion, a subgroup of patients with JRA who have not yet had an episode of MAS showed decreased NK function and an absence of circulating CD56^bright population, similar to the abnormalities observed in patients with MAS and HLH. This phenomenon was particularly common in the systemic form of JRA, a clinical entity strongly associated with MAS.

A phase I study of interleukin 12 with trastuzumab in patients with human epidermal growth factor receptor-2-overexpressing malignancies: analysis of sustained interferon gamma production in a subset of patients

PURPOSE

On the basis of preclinical studies, we hypothesized that interleukin (IL)12 would potentiate the antitumor actions of an antihuman epidermal growth factor receptor-2 (HER2) monoclonal antibody (trastuzumab). We conducted a Phase I trial to determine the safety and optimal biological dose of IL-12 when given in combination with trastuzumab.

PATIENTS AND METHODS

Patients with metastatic HER2-positive malignancies received trastuzumab on day 1 of each weekly cycle. Beginning in week 3, patients also received intravenous injections of IL-12 on days 2 and 5. The IL-12 component was dose-escalated within cohorts of 3 patients (30, 100, 300, or 500 ng/kg). Correlative assays were conducted using serum samples and peripheral blood cells obtained during the course of therapy.

RESULTS

Fifteen patients were treated, including 12 with HER2 2+ or 3+ breast cancer. The regimen was well tolerated with IL-12-induced grade 1 nausea and grade 2 fatigue predominating. Evaluation of dose-limiting toxicity and biological end points suggested that the 300 ng/kg dose was both the maximally tolerated dose and the optimal biological dose of IL-12 for use in combination with trastuzumab. Two patients with HER2 3+ breast cancer within the 500 ng/kg dose level experienced grade 1 asymptomatic decreases in left ventricular ejection fraction of 12% and 19% after 3 and 10 months of therapy, respectively. There was one complete response in a patient with HER2 3+ breast cancer metastatic to the axillary, mediastinal, and supraclavicular nodes, and 2 patients with stabilization of bone disease lasting 10 months and >12 months, respectively. Correlative assays showed sustained production of interferon (IFN)gamma by natural killer cells only in those patients experiencing a clinical response or stabilization of disease. Elevated serum levels of macrophage inflammatory protein-1alpha, tumor necrosis factor-alpha, and the antiangiogenic factors IFN-gamma inducible protein-10 and monokine induced by gamma were also observed in these patients. Patient genotyping suggested that a specific IFN-gamma gene polymorphism might have been associated with increased IFN-gamma production. The ability of patient peripheral blood cells to conduct antibody-dependent cellular cytotoxicity against tumor targets in vitro did not correlate with clinical response or dose of IL-12.

CONCLUSIONS

The addition of IL-12 to trastuzumab therapy did not appear to enhance the efficacy of this antibody treatment. Sustained production of IFN-gamma and other cytokines were observed in three patients: One who exhibited a complete response and two others who had stabilization of disease lasting over 6 months. Given the small sample size and heterogeneity of the patient population, the effects of IL-12 on the innate immune response to trastuzumab therapy should be further explored in the context of a larger clinical trial.

Perforin expression in peripheral blood lymphocytes and skin-infiltrating cells in patients with lichen planus

BACKGROUND

Current evidence suggests that lichen planus is a T-cell-mediated autoimmune disease in which cytotoxic mechanisms have been poorly investigated.

OBJECTIVES

We investigated the expression of perforin in subpopulations of peripheral blood lymphocytes (PBL) in exacerbation and remission phases of the disease as well as in skin lesions.

METHODS

We performed a simultaneous detection of perforin (intracellular molecule) and cell surface antigens on PBL by flow cytometry, and skin lesions were investigated by immunohistochemistry.

RESULTS

The most interesting finding was a significant increase of perforin expression in cytotoxic T lymphocytes (CD3+ perforin+ cells) in the exacerbation phase of disease (P < 0.05), which was mostly located in the CD8+ subpopulation (CD8+ perforin+) (P < 0.01). Using immunohistochemistry we confirmed the infiltration of T lymphocytes in skin lesions, especially of CD4+ and CD8+ phenotypes, compared with uninvolved (P < 0.05) and healthy skin (P < 0.01). The expression of perforin was also significantly higher in lesional skin compared with nonlesional and healthy skin (P < 0.05).

CONCLUSIONS

Our results clearly show the upregulation of perforin expression in peripheral blood as well as in lesions of patients with lichen planus and therefore suggest an important role for perforin in this autoimmune disease.

Analysis of Murine Natural Killer Cell Microsomal Proteins Using Two-Dimensional Liquid Chromatography Coupled to Tandem Electrospray Ionization Mass Spectrometry

This study describes the application of a single tube sample preparation technique coupled with multidimensional fractionation for the analysis of a complex membrane protein sample from murine natural killer (NK) cells. A solution-based method that facilitates the solubilization and tryptic digestion of integral membrane proteins is conjoined with strong cation exchange (SCX) liquid chromatography (LC) fractionation followed by microcapillary reversed-phase (microRP) LC tandem mass spectrometric analysis of each SCXLC fraction in second dimension. Sonication in buffered methanol solution was employed to solubilize, and tryptically digest murine NK cell microsomal proteins, allowing for the large-scale identification of integral membrane proteins, including the mapping of the membrane-spanning peptides. Bioinformatic analysis of the acquired tandem mass spectra versus the murine genome database resulted in 11,967 matching tryptic peptide sequences, corresponding to 5782 unique peptide identifications. These peptides resulted in identification of 2563 proteins of which 876 (34%) are classified as membrane proteins.

Differential expression of granzymes A and B in human cytotoxic lymphocyte subsets and T regulatory cells

Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells use the perforin/granzyme pathway as a major mechanism to kill pathogen-containing cells and tumor cells.(1,2) Dysregulation of this pathway results in several human diseases, such as hemophagocytic lymphohistiocytosis. Here we characterize the single-cell expression pattern of granzymes A and B in human lymphocytes using a flow cytometry-based assay. We demonstrate that most circulating CD56(+)8(-) NK cells, and approximately half of circulating CD8(+) T lymphocytes, coexpressed both granzymes A and B. In contrast, few circulating CD4(+) T lymphocytes expressed granzymes A or B. Activation of CD8(+) T lymphocytes with concanavalin A (ConA)/interleukin-2 (IL-2), and activation of CD4(+) T lymphocytes with antibodies to CD3/CD28 or CD3/CD46 (to generate T regulatory [Tr1] cells), induced substantial expression of granzyme B, but not granzyme A. Naive CD4(+)CD45RA(+) cells stimulated with antibodies to CD3/CD46 strongly expressed granzyme B, while CD3/CD28 stimulation was ineffective. Finally, we show that granzyme B-expressing CD4(+) Tr1 cells are capable of killing target cells in a perforin-dependent, but major histocompatibility complex (MHC)/T-cell receptor (TCR)-independent, manner. Our results demonstrate discordant expression of granzymes A and B in human lymphocyte subsets and T regulatory cells, which suggests that different granzymes may play unique roles in immune system responses and regulation.

Proteomic investigation of natural killer cell microsomes using gas-phase fractionation by mass spectrometry

We have explored the utility of gas-phase fractionation by mass spectrometry (MS) in the mass-to-charge (m/z) dimension (GPF(m/z)) for increasing the effective number of protein identifications in cases where sample quantity limits the use of multi-dimensional chromatographic fractionation. A peptide digestate from proteins isolated from the membrane fraction of natural killer (NK) cells was analyzed by microcapillary reversed-phase liquid chromatography coupled online to an ion-trap (IT) mass spectrometer. Performing GPF(m/z) using eight narrow precursor ion scan m/z ranges enabled the identification of 340 NK cell proteins from 12 microg of digestate, representing more than a fivefold increase in the number of proteins identified as compared to the same experiment employing a standard precursor ion survey scan m/z range (i.e., m/z 400-2000). The results show that GPF(m/z) represents an effective technique for increasing protein identifications in global proteomic investigations especially when sample quantity is limited.

Determination of different forms of human interferon-γ in single natural killer cells by capillary electrophoresis with on-capillary immunoreaction and laser-induced fluorescence detection

A novel method for determining different forms of human interferon-gamma (IFN-gamma) in single natural killer cells was developed by capillary electrophoresis (CE) with on-capillary immunoreaction and laser-induced fluorescence (LIF) detection. Cells were perforated with digitonin and one single cell was electrokinatically introduced into the front end of a separation capillary. The monoclonal antibody labeled with fluorescein isothiocyanate of IFN-gamma was hydrodynamically injected into the front end of the capillary around the cell introduced. After the cell was lysed by ultrasonication, the front end of the capillary was used as a microreactor to allow different forms of IFN-gamma to process the immunoreaction with their labeled antibody. Finally, the complexes of different forms of IFN-gamma with their labeled antibody were separated and detected by CE with LIF detection with a limit of detection of zeptomoles (10(-21) mol).

The raft marker GM1 identifies functional subsets of granular lymphocytes in patients with CD3+ lymphoproliferative disease of granular lymphocytes

The raft marker GM1 is expressed at very low levels at the plasma membrane of resting T cells (GM1dull). In vitro T-cell activation induces synthesis of this lipid, which is then expressed at very high levels (GM1bright) at the membrane of activated/effector cells. By flow cytometry and confocal microscopy, we analyzed the expression and organization of GM1 in a series of 15 patients with CD3+ lymphoproliferative disease of granular lymphocytes (LDGL). We found that GM1bright GL were detectable in fresh blood samples obtained in all LDGL patients, although the range of brightly stained cells was extremely variable. This distinctive in vivo pattern has never been shown in T lymphocytes from healthy individuals or in patients with different chronic T or B lymphoproliferative disorders or active infectious diseases. The low number of cycling cells detected in LDGL patients was always included within the GM1bright GL population. Interestingly, GM1bright GL were demonstrated to contain a higher amount of IFN-gamma as compared to GM1dull GL. These findings allow to distinguish subsets of GL at different levels of activation within the monoclonal CD3+ population. The GM1bright GL subset is likely to be responsible for the renewing of GL and thus for maintaining chronic proliferation.

NKp46 defines a subset of bovine leukocytes with natural killer cell characteristics

Natural killer (NK) cells have not previously been precisely identified or characterized in cattle or any other ruminant species. We have generated a monoclonal antibody against bovine NKp46, which is expressed exclusively by NK cells in man. NKp46+ cells comprised 1-10% of blood mononuclear cells in cattle, and did not stain with antibodies against CD3, CD4, TCR1, B cell or granulocyte markers. The majority of the NKp46+ cells expressed CD2, and a variable fraction also expressed CD8. The tissue distribution of NKp46+ cells in cattle was compatible with the tissue distribution of NK cells in other species. Bovine NKp46+ cells had typical, large granular lymphocyte morphology, and proliferated vigorously in response to bovine IL-2 for a limited number of cell divisions. IL-2-activated NKp46+ cells killed the bovine kidney cell line MDBK. This cytotoxicity was inhibited by preincubation with antibody against NKp46. In a redirected lysis assay, IL-2-activated NKp46+ cells killed the FcgammaR+ target cell line P815 after preincubation with antibody against NKp46. Together, these data indicate that bovine NKp46 is anactivating receptor and demonstrate the existence of a subset of leukocytes in cattle that, in terms of surface markers, morphology and function, represent NK cells.