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At least 307 records · Page 17Linked to original sources
PubMed1998

Expression of interleukin-6 (IL-6) receptor gene in acute myeloblastic leukemia and response of leukemic cells to exogenous IL-6. A comparative study between cell line cells and corresponding native cells.

As interleukin (IL-6) ahs been reported to have diverse effects on acute myeloblastic leukemia (AML) blast cell growth, we investigated whether the level of IL-6 receptor (IL-6R) expression by blast cells is associated with their susceptibility to proliferate in response to exogenous IL-6. For absolute quantification of IL-6R transcript numbers, we established a quantitative IL-6R reverse transcription polymerase chain reaction (RT-PCR) method with an internal RNA standard. In the present work, two types of AML blast cells were investigated, namely autonomously growing cell line cells (n = 8) and non cultured native blast cells (n = 20), including those from which the cell lines originate. The native blast cells expressed an average of 2.8 x 10(7) +/- 1.9 x 10(7) IL-6R transcripts in one microgram of total cellular RNA, whereas the expression by the cell line cells was significantly more abundant, the value being 8.3 x 10(7) +/- 2.8 X 10(7) (P < 0.001). The proliferation responses were evaluated by exposing the cells to IL-6 (1000 U/ml) in a clonogenic cell culture assay and, in the case of the cell line cells, in a long-term suspension culture assay as well. None of the autonomously growing cell lines responded to exogenous IL-6, whereas the native blast cell showed either stimulatory, inhibitory or neutral responses. Thus, the IL-6R expression level did not predict whether the cells proliferated in response to exogenous IL-6, which shows that IL-6R quantification cannot be used as a screening test prior to possibly applying this cytokine to clinical use in AML therapy.

Adolescent↗
PubMed1988

Artificial T cell:B cell conjugation. A unique approach to analyze weak cell-cell interactions.

An antibody response against a thymic-dependent Ag requires cognate recognition of the Ag by B and T cells. Functional T-B cell (T-B) interaction involves binding of Ag by B cell surface Ig, internalization and processing of Ag, expression of an Ag fragment in the context of Ia, binding of Ag/Ia by the TCR and binding of T cell-derived lymphokines by B cell lymphokine receptors. It is becoming increasingly evident that B and T cell accessory molecules also are involved in T-B interactions. To determine the role of accessory molecules in T-B collaboration, we have designed a system in which T-B interaction was artificially induced in the absence of carrier protein. TNP-modified, turkey gamma-globulin-specific, Th cells were allowed to form conjugates with TNP-specific B cells in the absence of hapten-carrier complex. Both B and T cells were induced to proliferate and B cells partially differentiated into antibody-secreting cells when B cells were cultured with TNP-modified but not unmodified T cells. The activation of B cells by TNP-modified T cells was not MHC restricted but was blocked by anti-Ia antibodies, suggesting a role for Ia distinct from Ag presentation. Furthermore, B cell proliferation was also inhibited by antibodies to L3T4 and LFA-1, suggesting a functional accessory role for these molecules in induction of B cell proliferation/differentiation.

Animals↗
PubMed1997

Absolute dependence of T cell receptor(hi) cell generation and relative dependence of T cell receptor(int) cell generation on the thymus.

Recent evidence indicates that conventional T cells are generated by the mainstream of T cell differentiation in the thymus and acquire a high density of T cell receptor expression (i.e. TCRhi). In contrast, primordial T cells (or NK1.1+ T cells) are generated by the extrathymic pathways or an alternative intrathymic pathway and express an intermediate density of TCR (i.e. TCRint). To obtain further evidence, it was examined how thymus grafting influenced the distribution of T cell populations in athymic nude mice. When BALB/c nu/nu mice were engrafted with thymocyte-depleted BALB/c+/+ fetal thymi, two changes emerged after grafting: nude mice generated TCRhi cells de novo in the periphery as well as in the grafted thymi, and the absolute number of interleukin-2 receptor beta chain+ TCRint cells increased prominently in number in the periphery. Among thymic hormones tested, the administration of thymosin alpha induced a slight expansion of CD3int cells in nude mice. To examine a possible interaction of TCRint cells with TCRhi cells in the periphery, B6 nu/nu mice (Ly5.2+) were injected with TCRhi cells purified from the spleen of B6 Ly5.1 congenic mice. In this case, TCRint (Ly5.2+) cells expanded well in all tested organs of nude mice. These results suggest that the generation of TCRhi cells is absolutely dependent on the thymus and that TCRint cells expand under the influence of the thymus (humoral) and due to interaction with thymus-derived conventional T cells.

Animals↗
PubMed1993

Glycoprotein B of human cytomegalovirus promotes virion penetration into cells, transmission of infection from cell to cell, and fusion of infected cells.

Human cytomegalovirus (HCMV) glycoprotein B (gB) is an abundant glycoprotein in the virion envelope that elicits neutralizing antibodies in human infection and in immunized animals. Using a panel of monoclonal antibodies to gB with neutralizing activity, we analyzed in detail the mechanisms by which these antibodies block HCMV infection. Twelve antibodies with complement-independent neutralizing activity were studied for their effect on the attachment of virions to the cell surface, virion penetration into cells, the transmission of infection from cell to cell, and fusion of infected cells. All of the complement-independent antibodies blocked penetration of virions into cells but had no effect on virion attachment to the cell surface. The most potent neutralizing antibodies also limited the spread of infection from cell to cell. Fusion of HCMV-infected U373 glioblastoma cells was blocked by all but two of the neutralizing antibodies to gB, suggesting that fusion of infected cells is similar but not identical to the fusion of the virion envelope with the cell membrane that occurs during virion entry. Our findings provide the first evidence that HCMV gB is a multifunctional glycoprotein that promotes virion penetration into cells, the transmission of infection from cell to cell, and fusion of infected U373 cells.

Antibodies, Monoclonal↗
PubMed1986

Lysis of small cell carcinoma of the lung tumor cell lines by gamma interferon-activated allogeneic peripheral blood mononuclear cells: abrogation of killing by pretreatment of tumor cells with gamma interferon.

Interferon has been shown to enhance the ability of nonspecific cytotoxic mononuclear cells to lyse some, but not all, tumor cells. We have examined the effect of recombinant human gamma interferon (rIFN gamma) on the cell-mediated cytolysis of tumor target cells derived from continuously cultured lines of small cell carcinoma of the lung (SCCL). Cells from the SCCL lines DMS 44, 53, 79, 92, and 406 were labeled with 51Cr and incubated with normal and rIFN gamma-stimulated peripheral blood mononuclear cells for 18 h at 37 degrees C and tumor cell lysis estimated by measuring 51Cr release. Although cells from certain SCCL lines were good targets for cell mediated cytotoxicity, susceptibility to lysis was heterogeneous among the different SCCL lines. DMS 406 and 79 were, on average, maximally lysed, while DMS 44, 53, and 92 showed less susceptibility to lysis by either control or rIFN gamma-stimulated effector cells. In addition, although pretreatment with rIFN gamma increased the cytolytic capacity of normal peripheral blood mononuclear cells from several different donors, preincubation of the tumor cell lines with rIFN gamma resulted in inhibition of cytolysis mediated by both control and IFN-activated effector cells. These findings suggest that although rIFN gamma may enhance cell-mediated lysis of SCCL tumor cells, it may also decrease susceptibility to lysis.

Antigens, Surface↗
PubMed2001

Identification of the T cell clones expanding within both CD8(+)CD28(+) and CD8(+)CD28(-) T cell subsets in recipients of allogeneic hematopoietic cell grafts and its implication in post-transplant skewing of T cell receptor repertoire.

We have previously reported that skewed repertoires of T cell receptor-beta chain variable region (TCRBV) and TCR-alpha chain variable region (TCRAV) are observed at an early period after allogeneic hematopoietic cell transplantation. Furthermore, we found that T lymphocytes using TCRBV24S1 were increased in 28% of the recipients of allogeneic grafts and an increase of TCRBV24S1 usage was shown to result from clonal expansions. Interestingly, the arginine residue was frequently present at the 3' terminal of BV24S1 segment and was followed by an acidic amino acid residue within the CDR3 region. These results suggest that these clonally expanded T cells are not randomly selected, but are expanded by stimulation with specific antigens. This study was undertaken to elucidate the mechanisms of the post-transplant skewing of TCR repertoires. Since the CD8(+)CD28(-)CD57(+) T cell subset has been reported to expand in the peripheral blood of patients receiving allogeneic hematopoietic cell grafts, we examined the TCRAV and TCRBV repertoires of the CD8(+)CD28(-) T cell and CD8(+)CD28(+) T cell subsets, and also determined the clonality of both T cell populations. In all three recipients examined, the CD8(+)CD28(-) T cell subset appeared to define the post-transplant TCR repertoire of circulating blood T cells. Moreover, the CDR3 length of TCRBV imposed constraints in both CD8(+)CD28(-) T cell and CD8(+)CD28(+) T cell subsets. The DNA sequences of the CDR3 region were determined, and the same clones were identified within both CD8(+)CD28(-) and CD8(+)CD28(+) T cell subsets in the same individuals. These results suggest that the clonally expanded CD8(+)CD28(-) T cells after allogeneic hematopoietic cell transplantation derive from the CD8(+)CD28(+) T cell subset, possibly by an antigen-driven mechanism, resulting in the skewed TCR repertoire.

Amino Acid Sequence↗
PubMed2005

Contact stimulation of prostate cancer cell migration: the role of gap junctional coupling and migration stimulated by heterotypic cell-to-cell contacts in determination of the metastatic phenotype of Dunning rat prostate cancer cells.

BACKGROUND INFORMATION: Motile activity of tumour cells is regarded as a critical factor determining their metastatic potential. We have shown previously that contrary to the majority of normal cells, homotypic contacts between some tumour cells, among them low metastatic (AT-2) and highly metastatic (MAT-LyLu) rat prostate cancer cells, increase the speed of their movements. The aim of the present study was to determine the effect of heterotypic cell-to-cell contacts on the migration of rat prostate cancer cells differing in metastatic potential, and to correlate it with the intensity of homo- and heterologous gap junctional coupling. RESULTS: MAT-LyLu and AT-2 cells moving on the surface of fibroblasts displayed significantly greater cell displacement than those moving on plastic substrata. This effect correlated with the polarization (contact guidance) and increased speed of cell movements. However, in contrast with the migration on plastic substrata, where MAT-LyLu cells displayed considerably higher motility than AT-2 cells, no differences between both cell lines were observed on the surface of fibroblasts. On the other hand, in contrast with AT-2, Mat-LyLu cells displayed extensive homologous coupling mediated by connexin43 and were able to couple with normal fibroblasts. CONCLUSION: Heterotypic contacts between migrating prostatic cancer cells and normal fibroblasts can strongly stimulate their migration during invasion; however, this effect does not correlate with the gap junctional coupling between cancer cells and normal fibroblasts.

Animals↗
PubMed1996

Signal transduction through mu kappa B-cell receptors expressed on pre-B cells is different from that through B-cell receptors on mature B cells.

We introduced kappa light chain genes into pre-B cells to increase the surface mu HC expression, and established transfectants expressing mature type of B-cell receptors (BCR) on pre-B-cell surfaces. Since the cytoplasmic conformations of the reconstituted BCR and intrinsic pre-B-cell receptor (pre-BCR) are identical, they would be connected with the identical signal transduction pathways in pre-B cells. By using the transfectants, we revealed that the reconstituted BCR on pre-B cells was functionally equivalent to BCR on mature B cells in terms of the induction of intracellular Ca++ mobilization. However, we found that the signal-transduction pathways through BCR on pre-B cells were quantitatively different from those mature B cells in two ways. First, cross-linkage of the reconstituted BCR on pre-B cells induced preferential tyrosine phosphorylation of p120 and p100, which was not observed when BCR on mature B cells was cross-linked. Second, BCR in pre-B cells was physically associated with a larger amount of phosphatidylinositol-3 kinase (PI-3K) than BCR in mature B cells in spite of the fact that both pre-B and B cells expressed a similar amount of PI-3K in cytoplasm. Signals through pre-BCR and BCR are known to cause distinct biological effects in B-cell development. The biochemical features in the downstream of reconstituted BCR on pre-B cells, which we revealed in this study, will be of help in understanding the mechanism of functional differences between pre-BCR and BCR.

B-Lymphocytes↗
PubMed1998

PDGF, TGF-beta, and heterotypic cell-cell interactions mediate endothelial cell-induced recruitment of 10T1/2 cells and their differentiation to a smooth muscle fate.

We aimed to determine if and how endothelial cells (EC) recruit precursors of smooth muscle cells and pericytes and induce their differentiation during vessel formation. Multipotent embryonic 10T1/2 cells were used as presumptive mural cell precursors. In an under-agarose coculture, EC induced migration of 10T1/2 cells via platelet-derived growth factor BB. 10T1/2 cells in coculture with EC changed from polygonal to spindle-shaped, reminiscent of smooth muscle cells in culture. Immunohistochemical and Western blot analyses were used to examine the expression of smooth muscle (SM)-specific markers in 10T1/2 cells cultured in the absence and presence of EC. SM-myosin, SM22alpha, and calponin proteins were undetectable in 10T1/2 cells cultured alone; however, expression of all three SM-specific proteins was significantly induced in 10T1/2 cells cocultured with EC. Treatment of 10T1/2 cells with TGF-beta induced phenotypic changes and changes in SM markers similar to those seen in the cocultures. Neutralization of TGF-beta in the cocultures blocked expression of the SM markers and the shape change. To assess the ability of 10T1/2 cells to contribute to the developing vessel wall in vivo, prelabeled 10T1/2 cells were grown in a collagen matrix and implanted subcutaneously into mice. The fluorescently marked cells became incorporated into the medial layer of developing vessels where they expressed SM markers. These in vitro and in vivo observations shed light on the cell-cell interactions that occur during vessel development, as well as in pathologies in which developmental processes are recapitulated.

Animals↗
PubMed1977

A requirement for trypsin-sensitive cell-surface components for cell-cell interactions of embryonic neural retina cells.

A quantitative assay was used to measure the rate of collection of a population of embryonic neural retina cells to the surface of cell aggregates. The rate of collection of freshly trysinized cells was limited in the initial stages by the rate of replacement of trypsin-sensitive cell- surface components. When cells were preincubated, or "recovered," and then added to cell aggregates, collection occurred at a linear rate and was independent of protein and glycoprotein synthesis. The adhesion of recovered cells was temperature and energy dependent, and was reversibly inhibited by cytochalasin B. Colchicine had little effect on collection of recovered cells. Antiserum directed against recovered cell membranes was shown to bind to recovered cells by indirect immunofluorescence. The antiserum also was shown to inhibit collection of recovered cells to aggregates, suggesting that at least some of the antigens identified might be involved in the adhesion process. The inhibitory effect of the antiserum was dose dependent . Freshly trypsinized cells absorbed neither the immunofluorescence activity nor the adhesion-inhibiting activity. Recovered cells absorbed away both activities. In specificity studies, dorsal neural retina cells adhered to aggregates of ventral optic tectum in preference to aggregates of dorsal optic tectum. The adhesive specificity of the dorsal retina cells was less sensitive to trypsin than the adhesive specificity of ventral retina cells which adhered preferentially to dorsal tectal aggregates only after a period of recovery.

Animals↗
PubMed1989

Correlation between cell-cell contact formation and activation of protein kinase C in a human squamous cell carcinoma cell line.

Formation of desmosomal cell-cell contact associated with reorganization of keratin intermediate filaments (KIFs) was observed when cultured cells of a cell line of human skin squamous cell carcinoma were transferred from low (0.07 mM) calcium to high (1.87 mM) calcium medium. At low calcium, cells were dispersed without desmosomal cell-cell contact and the KIFs were mostly concentrated around the nucleus. After 15 min of the transfer, cells contacted each other and formed small colonies and the KIFs initiated to show a radial arrangement. In addition to the cell-cell contact formation and rearrangement of KIFs, the transfer induced fourfold increase of particulate-associated protein kinase C (C-kinase) activity. When 12-O-tetradecanoyl phorbol-13-acetate (PMA), which specifically activates C-kinase, was added to the cells grown at low calcium medium, cell-cell contact formation and radial arrangement of KIF bundles almost identical to those induced by the transfer to high calcium medium were observed. These data suggest a correlation between an increase in C-kinase activity and formation of cell-cell contacts associated with rearrangements of KIFs.

Calcium↗
PubMed2004

[Combined cell therapy by using dendritic cells, T-cells and NK cells to human polymorphic cancer].

Although an expression of MHC molecules and tumor associated antigens of the cancer are not uniform, we consider that the cancer immunotherapy for some specific tumor antigens cannot correspond to molecular biological varieties of the cancer. Consequently, we tried to develop a method to separate dendritic cells (DC), T-cells and natural killer (NK) cells from peripheral blood mononuclear cells (PBMC) obtained from healthy volunteers. PBMC were separated by centrifugation on Ficoll-Hypaque gradients from peripheral blood obtained from healthy volunteers. After separating these cells, the cells were put into a plastic flask, and we isolated monocyte fraction (dendritic cells), NK cell fraction and T-cell fraction one after another by the difference in its ability to adhere to a plastic flask. We analyzed surface markers and activation states of these groups. We could induce dendritic cells from the monocyte fraction, CD3-activated T-cells (CAT) from the T-cell fraction, and adherent lymphokine activated-killer cells (A-LAK) from the NK cell fraction. Therefore, we indicate the possibility of the combined cell therapy with three immune cell fractions in which we can induce from the same blood at once.

Antigens, Surface↗
PubMed1997

Human sunlight-induced basal-cell-carcinoma-associated dendritic cells are deficient in T cell co-stimulatory molecules and are impaired as antigen-presenting cells.

Immune surveillance of skin cancer involves the stimulation of effector T cells by tumor-derived antigens and antigen-presenting cells (APCs). An effective APC must not only display processed antigen in the context of MHC molecules but also express co-stimulatory molecules that are required to fully activate T cells. One of the most common cutaneous neoplasms is basal cell carcinoma. To investigate expression of the co-stimulatory molecules CD80 (B7-1) and CD86 (B7-2) on tumor-associated dendritic cells (TADCs), cryosections from basal cell carcinomas were immunostained. In basal cell carcinomas, only 1 to 2% of intratumor and 5 to 10% of peritumor APCs expressed CD80 or CD86. In contrast, biopsies of immunological/inflammatory dermatoses revealed that 38 to 73% of APCs expressed CD80 and CD86. To further evaluate their phenotype and function, TADCs were isolated from tissue samples of basal cell carcinomas; they were non-adherent to plastic, displayed a typical dendritic morphology, and expressed high levels of major histocompatibility class II molecules on their surface. When TADCs were compared with dendritic cells from blood for presentation of superantigens (staphylococcal enterotoxins A and B) to resting autologous T cells, TADCs were consistently weaker stimulators of T cell proliferation than blood dendritic cells. When analyzed by flow cytometry, TADCs expressed high levels of HLA-DR, but only 5 to 10% co-expressed CD80 or CD86. A 3-day culture in granulocyte/macrophage colony-stimulating factor-containing medium partially reconstituted the TADC expression of CD80 and CD86 as well as their immunostimulatory capacity. Thus, in this common skin cancer, although there are prominent collections of HLA-DR-positive APCs in and around tumor cells, the TADCs are deficient in important co-stimulatory molecules as well as being weak stimulators of T cell proliferation. The paucity of co-stimulatory molecule expression and functional activity of TADCs may explain why the local T lymphocytic infiltrate fails to become fully activated to eradicate adjacent tumor cells. From a clinical perspective, these findings suggest a novel immunotherapeutic strategy targeting T cell co-stimulatory molecules on professional APCs in cutaneous oncology.

Antigen-Presenting Cells↗
PubMed1998

Fibroblast growth factor 2 uses PLC-gamma1 for cell proliferation and PI3-kinase for alteration of cell shape and cell proliferation in corneal endothelial cells.

PURPOSE: Fibroblast growth factor 2 (FGF-2) induces endothelial-mesenchymal modulation in corneal endothelial cells, including stimulation of cell proliferation and cell shape change and induction of fibrillar collagen. In the present study, we investigated whether FGF-2 uses distinct signaling pathways for individual biological activities. METHODS: Specific metabolic inhibitors were used to block cell proliferation, while reversion of cellular morphology (modulated with FGF-2) was determined using specific antibodies and inhibitors. Immunocytochemical analysis was performed to identify any changes observed in the cytoskeleton in relation to cell shape. Association of cytoskeleton molecules with phosphatidylinositol 3-kinase was determined using co-precipitation. Cell proliferation was assayed using a colorimetric method for determining the number of viable cells. RESULTS: The fibroblastic morphology induced by FGF-2 reverted to a polygonal shape in cells treated with anti-FGF-2 antibody, anti-phosphatidylinositol 3-kinase antibody, LY294002, and genistein, while anti-phospholipase C gamma1 antibody did not to reverse the modulated cell morphology. Cell proliferation mediated by FGF-2 was blocked by metabolic inhibitors (genistein, LY294002 and wortmannin); genistein inhibited FGF-mediated cell proliferation in a dose-response manner and had a maximum inhibition of 80% at 100 microM, while inhibitors of phosphatidylinositol 3-kinase had less inhibitory effect than did genistein. When cytoskeleton proteins were examined, the characteristic punctated staining profiles of vinculin observed in normal cells were maintained in fibroblastic corneal endothelial cells treated with FGF-2. The inhibitors that cause reversion of cell shape also demonstrated the punctated staining potential. Likewise, the staining profiles of alpha-actinin and smooth muscle alpha-actin were not altered, regardless of cell shape. Filamentous actin and alpha-actinin were co-localized to the cytoskeleton and phosphatidylinositol 3-kinase was associated with the cytoskeleton, regardless of cell shape. CONCLUSIONS: These findings indicate that FGF-2 uses distinct and/or dual signaling pathways for individual biological activities.

Androstadienes↗
PubMed1998

Protoporphyrin IX accumulation in cells treated with 5-aminolevulinic acid: dependence on cell density, cell size and cell cycle.

Human colon adenocarcinoma cells (WiDr) and Chinese hamster lung fibroblasts cells (V79) were incubated with different concentrations of 5-aminolevulinic acid (ALA), and the production of protoporphyrin IX (PpIX) was studied using several techniques. The amount of PpIX produced per cell increased with increasing ALA concentration according to different kinetics for the 2 cell lines. For both cell lines a cell density dependency of the PpIX synthesis was observed. For saturating ALA concentrations, 2-3 times more PpIX was produced per cell at a density of 5 x 10(4) than at a density of 5 x 10(3) cells/cm2. The photosensitivity of cells appeared to increase even more than the PpIX content, indicating a cooperative effect in inactivation. The PpIX production rate increased with cell size and was about 1.9 times higher for cells in the G2 + M phase than for cells in the G1 phase of the cell cycle. Neither cell size nor cell cycle distribution were significantly dependent on cell density.

Adenocarcinoma↗
PubMed1978

Cell adhesion and cell surface topography in aggregates of 3T3 and SV40-virus-transformed 3T3 cells. Visualization of interior cells by scanning electron microscopy.

A technique for exposing the interior of aggregates of cultured cells has been developed and is described in this report. Using this technique, we have examined for the first time, by scanning electron microscopy, cell morphology and cell contact ultrastructure in the interior of aggregates of BALB/c 3T3 and SV40-transformed 3T3 cells. The 3T3 cells make initial intercellular contact by means of microvillar processes. Over a period of 3-8 h, some of these microvillar contacts are replaced by broader projections. In contrast, the SV40-transformed cells make initial intercellular contact by means of blebs or blunt projections which are also broadened and extended over a period of 3-8 h. For both 3T3 and SV40-3T3 cells, the surfaces of the cells which form the outer layer of the aggregate resemble the surfaces of single cells fixed in suspension, regardless of how long the aggregates have been cultured. Thse cells are covered with many cellular processes and are roughly hemispherical in profile. The surfaces of the internal cells of the aggregates, however, lose many of their cellular processes, develop smooth patches, and many become irregular in shape. This smooth morphology was also observed on the interior surfaces of the peripheral cell layer. From these observations we conclude that: (a) the stabilization of adhesive contacts is a slow process which takes at least 3-8 h; (b) the outer surfaces of peripheral cells differ significantly from the surfaces of interior cells; and (c) clear differences in surface topography exist between nonmalignant 3T3 cells and their malignant SV40 transformants.

Cell Adhesion↗
PubMed2006

Natural killer cell and hepatic cell interaction via NKG2A leads to dendritic cell-mediated induction of CD4 CD25 T cells with PD-1-dependent regulatory activities.

Natural killer (NK) cells have the ability to control dendritic cell (DC)-mediated T cell responses. However, the precise mechanisms by which NK receptor-mediated regulation of NK cells determines the magnitude and direction of DC-mediated T cell responses remain unclear. In the present study, we applied an in vitro co-culture system to examine the impact of NK cells cultured with hepatic cells on DC induction of regulatory T cells. We found that interaction of NK cells and non-transformed hepatocytes (which express HLA-E) via the NKG2A inhibitory receptor resulted in priming of DCs to induce CD4(+) CD25(+) T cells with regulatory properties. NKG2A triggering led to characteristic changes of the cytokine milieu of co-cultured cells; an increase in the transforming growth factor (TGF)-beta involved in the generation of this specific type of DC, and a decrease in the tumour necrosis factor-alpha capable of antagonizing the effect of TGF-beta. The regulatory cells induced by NK cell-primed DCs exert their suppressive actions through a negative costimulator programmed death-1 (PD-1) mediated pathway, which differs from freshly isolated CD4(+) CD25(+) T cells. These findings provide new insight into the role of NK receptor signals in the DC-mediated induction of regulatory T cells.

Cell Communication↗
PubMed2001

Broad distribution of colony-forming cells with erythroid, myeloid, dendritic cell, and NK cell potential among CD34(++) fetal liver cells.

The generation of erythroid, myeloid, and lymphoid cells from human fetal liver progenitors was studied in colony-forming cell (CFC) assays. CD38(-) and CD38(+) progenitors that expressed high levels of CD34 were grown in serum-deprived medium supplemented with kit ligand, flk2/flt3 ligand, GM-CSF, c-mpl ligand, erythropoietin, and IL-15. The resulting colonies were individually analyzed by flow cytometry. CD56(+) NK cells were detected in 21.9 and 9.9% of colonies grown from CD38(-) and CD38(+) progenitors, respectively. NK cells were detected in mostly large CD14(+)/CD15(+) myeloid colonies that also, in some cases, contained red cells. NK cells were rarely detected in erythroid colonies, suggesting an early split between the erythroid and the NK cell lineages. CD1a(+) dendritic cells were also present in three-quarters of the colonies grown from CD38(-) and CD38(+) progenitors. Multilineage colonies containing erythrocytes, myeloid cells, and NK cells were present in 13.7 and 2.7% of colonies grown from CD38(-) and CD38(+) progenitors, respectively. High proliferative-potential CFCs that generated multilineage colonies were also detected among both populations of progenitors. The total number of high proliferative-potential CFCs with erythroid, myeloid, and NK cell potential was estimated to be 2-fold higher in the CD38(+) fraction compared with the CD38(-) fraction because of the higher frequency of CD38(+) cells among CD34(++) cells. The broad distribution of multipotent CFCs among CD38(-) and CD38(+) progenitors suggests that the segregation of the erythroid, myeloid, and lymphoid lineages may not always be an early event in hemopoiesis. Alternatively, some stem cells may be present among CD38(+) cells.

ADP-ribosyl Cyclase↗