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Z Brahmi

Publications and source records attributed to Z Brahmi.

At least 73 records · Page 4Linked to original sources
PubMed1984

Compared mechanisms of tumor cytolysis by human natural killer cells and activated polymorphonuclear leukocytes.

The mechanism(s) of natural killer (NK) cell-mediated cytotoxicity (CMC) remains largely unknown. In this study, we investigated the possibility of human NK cells to exhibit an oxidative burst (OB) after stimulation by K562, an NK-sensitive target cell (TC). The addition of catalase (CAT) or superoxide dismutase (SOD) to the NK-mediated cytotoxic assay had no effect on NK-CMC. In contrast, CAT and SOD effectively modulated the cytotoxicity mediated by phorbol-12-myristate-13-acetate (PMA)-activated polymorphonuclear leukocytes (PMNL) against three different tumor TC, including K562. CAT abrogated, while SOD enhanced PMA-activated PMNL-mediated cytotoxicity. The synergistic effect of SOD and PMA was suppressed in a dose-dependent fashion by CAT. Furthermore, by chemiluminescence (CL) and SOD-inhibitable reduction of cytochrome c, we failed to detect an OB associated with K562-stimulated NK cells. PMNL, however, rapidly responded to PMA (10 ng/ml), generating almost 10(6) cpm within 20 min and 26.7 nM O-2/10(6) cells/30 min, as detected by CL and reduction of cytochrome c, respectively. Finally, K562 alone, at cell concentrations corresponding to effector cell:target cell (EC:TC) ratios of 1:1 and 1:10, reduced cytochrome c, but this reduction was not inhibited by SOD, thus suggesting a diaphorase activity. Overall, we show that: a) tumor cell destruction by human NK cells and by PMA-activated PMNL is mediated by different mechanisms; and b) NK-CMC against a sensitive TC does not involve an OB.

Catalase↗
PubMed1983

Immunologic studies of three family members with the immunodeficiency with hyper-IgM syndrome.

We report the results of immunologic studies in a family in which the father (III-5) and his two daughters (IV-7 and IV-8) had the hyper-IgM syndrome (IHIS). Repeated immunoglobulin levels done on III-5 showed a typical IHIS pattern: low IgG, traces of IgA, and high IgM. IV-7, who also had stage IIA Hodgkin's disease, had a similar pattern except after irradiation therapy to sites of disease, when IgM dropped to normal range while IgG and IgA remained low. IV-8, on the other hand, had normal IgG and IgA and moderately elevated IgM until age 18 months, when she gradually developed the IHIS pattern. All three patients had normal numbers of B cells (sIg) and of T cells, although IV-7 had increased suppression. Finally, all three patients shared the A3,B7 haplotype and none was blood type O. IHIS is not necessarily X linked, is not associated with blood type O, and appears to be heterogeneous even within the same family. Inheritance in this family is apparently autosomal dominant and the father may represent a new mutation.

Adult↗
PubMed1983

Mechanism of action of phorbol myristate acetate on human natural killer cell activity.

We have investigated the kinetics of inhibition and regeneration of human natural killer (NK) cell-mediated lysis of K562, a human erythroleukemia cell line, by the potent tumor-promoting agent phorbol-12-myristate-13-acetate (PMA). It is shown that PMA inhibits NK cell-mediated cytotoxicity (CMC) in a dose-dependent manner whether the compound is present throughout the 4-hr cytotoxic assay or the effector cells (EC) are pretreated with PMA. Pretreatment of the target cells (TC) with PMA produced a different profile of NK activity suggesting that PMA inhibition of NK-CMC is primarily due to the inactivation of EC. PMA-induced inhibition of NK-CMC does not affect TC binding and is not circumvented by compounds that enhance intracellular levels of cyclic guanosine monophosphate (cGMP) or calcium. Furthermore, and contrary to a recent report, PMA-induced inhibition of NK-CMC is independent of monocytes. Finally, kinetic studies revealed that PMA-induced inhibition of NK-CMC occurs rapidly and is fully reversible provided that "regenerated EC" are thoroughly washed, prior to the cytotoxic assay, to rid the cell suspension of residual PMA. The potential implications of these results to the currently accepted theory of TC destruction by NK cells, the stimulus-secretion model, are discussed.

Calcimycin↗
PubMed1983

Studies on the mechanism of human natural killer cell-mediated cytolysis. I. Modulation by dexamethasone and arachidonic acid.

Natural killer (NK) cell-mediated cytotoxicity, as measured by the lysis of the human erythroleukemic cell line K562, is inhibited by the glucocorticosteroid dexamethasone (DEX). Kinetic analysis revealed that DEX inhibits an early event(s) in the lytic mechanism and that the inhibition is both transient and readily reversible if DEX is removed. The inhibition is not due to the production of a DEX-induced inhibitory protein or decreased target-cell binding. Attempts to counter the effects of DEX through the addition of inducers of NK activity were unsuccessful. Neither the calcium ionophore A23187 nor exogenous cyclic GMP was able to reverse the inhibition by DEX. The addition of arachidonic acid (AA), a pharmacologically active metabolite of phospholipase A-2 activation, was also unsuccessful in reversing the effects of DEX. In fact, AA itself inhibited NK activity in a dose-dependent fashion. This inhibition was not due to reduced target binding and was observed even in the presence of indomethacin. It is concluded that DEX blocks an early membrane-signaling event necessary to activate the lytic mechanism and that inhibition was not through some alternative mechanism. Inhibition of NK activity by arachidonic acid is not yet understood but most likely is not a result of enhanced prostaglandin synthesis. Hence, the study of DEX and AA inhibition provides a new approach to unravel some of the intricacies surrounding NK-mediated tumor target destruction.

Arachidonic Acid↗
PubMed1983

Nature of natural killer cell hyporesponsiveness in the Chediak-Higashi syndrome.

Two unrelated Chediak-Higashi syndrome (CHS) patients in the prelymphomatous phase and their families were tissue typed and tested for their immune functions including natural killer cell (NK) activity. NK activity was assessed by the conventional 4 hr chromium release assay and by a newly developed single cell liquid cytotoxic assay (SLA). SLA permits the simultaneous study of the overall binding of peripheral blood mononuclear cells (PMNC) to the targets and the number of lytic conjugates. As expected, both CHS patients had low NK activity although their family members, including an HLA-identical sibling, were well within normal range. When tested with SLA, the percent total binding of the patient's PMNC was normal, but the number of lytic conjugates was lower than the normal controls. None of the patients had the A3,B7 haplotype which had been previously implicated in NK-hyporesponsiveness. T (including T helper and T suppressor cells) and B lymphocyte functions were normal (as assessed by mitogen stimulation, mixed lymphocyte reaction, and immunoglobulin synthesis). Our results suggest that CHS: (1) is not due to impaired target binding, and (2) is mainly due to low lytic efficiency of mature NK cells.

Chediak-Higashi Syndrome↗
PubMed1983

Immunoglobulin M and G histoplasmal antibody response in histoplasmosis.

Radioimmunoassays for IgM and IgG histoplasmal antibodies were developed and proved to be specific for their respective immunoglobulin classes, sensitive, and reproducible. Elevated IgM antibodies were detected in 59.8% of patients with histoplasmosis and 7.9% of control subjects. Elevated IgG antibodies occurred in 80.4% of patients with histoplasmosis but in only 12.9% of control subjects. Radioimmunoassay was nearly twice as sensitive as complement fixation for identifying patients with mild, presumably asymptomatic, infection. Of 13 patients with serologic follow-up at least 1 yr later, elevated IgM antibodies cleared, whereas IgG antibodies persisted in 7. In an epidemiologic investigation of a recurrent histoplasmosis outbreak, only the radioimmunoassay was able to prove the hypothesis that construction for a swimming complex was the source of exposure. These assays promise to be useful for clinical and epidemiologic investigations.

Antibodies, Fungal↗
PubMed1982

A comparative study on the specificity of Androctonus australis (Saharan scorpion) and Limulus polyphemus (horseshoe crab) agglutinins.

The specificities of Limulus polyphemus and Androctonus australis sera were compared by agglutination and agglutination-inhibition micromethods with human untreated and enzyme-treated peripheral blood cells (erythrocytes, normal lymphocytes and chronic lymphocytic leukemia lymphocytes). Androctonus sera give higher titers than Limulus sera with erythrocytes and lymphocytes. Both sera show more avidity for leukemic than for normal lymphocytes. Limulus sera fail to agglutinate neuraminidase-treated cells but Androctonus sera react with untreated and neuraminidase-treated erythrocytes at the same degree. Sialyl-lactose is the best inhibitor for Androctonus sera, followed by N-acetylneuraminic and N-glycolylneuraminic acids, glucuronic and galacturonic acids, N-acetyl-D-glucosamine and N-acetyl-D-galactosamine. The amounts of inhibitor required depend upon the particular cell and enzyme treatment: agglutination of neuraminidase-treated erythrocytes by Androctonus is inhibited by lower concentrations of the same compounds that inhibit untreated erythrocytes agglutination. Results suggest that although Limulus and Androctonus have specificity for sialic acid containing compounds, on the cell surface, the Limulus receptors might be different from Androctonus receptors.

Agglutination↗
PubMed1975

Partial characterization of human histaminopectic factor.

Sera from normal human subjects are pooled and fractions are isolated by salt precipitation. The fraction responsible for agglutinating histamine bound latex particles is further purified by column chromatography. The histaminopectic activity can thus be traced to a single protein present in the IgG fraction of normal human serum. Its absence or the presence of an inhibitor in serum from allergic subjects is also sought as well as correlations between plasma concentrations of known immunoglobulins and specific histaminopectic activity. Some of its physical-chemical properties are explored. Evidence was also presented pointing to the possible presence of an inhibitor of the histaminopectic factor in human atopic serum.

Agglutinins↗
PubMed1970

Duplicate plating of immune cell products: analysis of globulin class secretion by single cells.

Antibodies secreted by individual immune cells were collected focally in very thin "original" and "imprint" layers of agar containing the target antigen, sheep erythrocytes. Identical treatment of both layers led to mirror image patterns of hemolytic plaques. Development of one layer for immunoglobulin M hemolysins and the other for immunoglobulin G hemolysins produced unrelated plaque patterns indicating that few, if any, cells simultaneously release substantial amounts of both gammaM and gammaG antibodies.

Animals↗
PubMedDate not supplied

Target cell-induced perforin mRNA turnover in NK3.3 cells is mediated by multiple elements within the mRNA coding region.

We have previously shown that in cytolytic cells exposed to sensitive targets the mRNA of the cytolytic protein perforin undergoes rapid downregulation. We now demonstrate that perforin message undergoes accelerated turnover in NK3.3 cells exposed to sensitive TC. This inducible mRNA decay phenomenon is specific for cytolytic protein messages, as levels of the constitutive message beta-actin are unchanged. This TC-induced perforin mRNA turnover cannot be attributed to a blockage of RNA synthesis, or to a rapid half-life (t 1/2). To determine the region(s) within the perforin transcript responsible for governing this TC-mediated turnover event, various segments of the perforin cDNA were cloned and inserted into the 3' UTR of rabbit beta globin (RG). Constructs containing perforin coding region cDNA, but not 3' UTR cDNA, mediated TC-induced mRNA turnover. These data indicate that multiple elements governing perforin mRNA stability reside within the coding region, a novel type of mRNA regulation not previously described.

Animals↗
PubMedDate not supplied

Mechanism of K562-induced human natural killer cell inactivation using highly enriched effector cells isolated via a new single-step sheep erythrocyte rosette assay.

In this study, we used preparations highly enriched in human natural killer (NK) cells to further characterize the mechanism of target-cell-induced NK inactivation. Highly enriched populations of NK cells were obtained by a newly developed, single-step sheep red blood cell rosette assay. This method, which did not require any incubation steps to facilitate cell contact, permitted a rapid and efficient isolation of NK cells from adherent-cell-depleted peripheral blood lymphocytes. The non-rosetted cells had high NK activity, possessed large granular lymphocyte (LGL) morphology and expressed the NK-associated antigens Leu-11a, Leu-7, OKM1 and NKH-1. In contrast, the rosetted cells had significantly lower NK activity, possessed typical lymphocyte morphology and expressed the T-cell-associated marker OKT3. Next, we examined the ability of these NK-enriched effector cells (ECc) to become inactivated by K562. Functional studies revealed that ECc lost greater than or equal to 95% of their lytic capacity following incubation with K562 at a ratio of 2/1 for 6 h. However, to achieve this level of inactivation, it was essential that the cell suspension be gently mixed every 90-120 min. Inactivation was not due to cell death and did not reflect changes in the percentages of cells bearing the Leu-11a, Leu-7, OKM1 and NKH-1 antigens, but was associated with an increase in cell surface concentration of OKM1. As judged by gross morphology, the percentages of LGL in ECc before and after treatment with K562 were essentially the same. Finally, K562-treated ECc also lost their ability to mediate antibody-dependent cellular cytotoxicity (ADCC), suggesting that both NK-cell-mediated cytotoxicity and ADCC may involve a common lytic pathway.

Animals↗
PubMedDate not supplied

High and low density PHA- (but not ConA-) activated T cells stimulate the autologous mixed lymphocyte reaction.

In this study, PHA- and ConA-activated cells (PAC and CAC) were used as stimulators in mixed lymphocyte reactions (MLR) using autologous (auto) and allogeneic (allo) peripheral mononuclear cells as responders. PAC, but not CAC, were stimulatory in allo- and auto-MLR, and this stimulation was not due to residual PHA. In PAC which have been activated for 96 h, auto-MLR was due to determinants present on low density T-cell blasts, while with PAC which had been stimulated for more than 192 h, the determinants seemed to be associated with high density T cells. Anti-T3 monoclonal antibodies and certain anti-DR suppressed auto- and allo-MLR mediated by PAC when present throughout the entire MLR assays. CAC suppressed PAC-mediated auto-MLR in a dose-dependent fashion. This inhibition was not DR-restricted and was reversed by the addition of exogenous IL-2. Our results indicate that: depending upon the length of activation, both low density and high density PHA-activated T cells exhibited strong stimulatory capacity in auto-MLR; ConA-activated T cells failed to stimulate auto- or allo-MLR and suppressed MLR mediated by PAC; this suppression was due to suppressor cells, not to suppressor factors, and was readily reversed by exogenous IL-2; pretreatment of CAC with anti-TAC did not reverse the inhibition.

Antigens, Differentiation, T-Lymphocyte↗
PubMedDate not supplied

Surface markers and biological functions of PMNC fractionated by countercurrent centrifugal elutriation.

Peripheral blood mononuclear cells (PMNC) were separated by countercurrent centrifugal elutriation (CCE) in PBS-EDTA medium into 13 fractions. Properties associated with B cells were restricted mainly to the first fractions (F2 and F4) while those associated with T cells were confined to fractions F4, F6 and F8. The final fraction (FF) contained more than 90% monocytes while fraction F10 contained 40% monocytes and 60% null cells, and F12 contained 50% monocytes and 50% null cells. Natural killer (NK) cell activity against K-562, a human erythroleukaemia cell line, and against an adherent undifferentiated sarcoma target, was distributed between fractions F6 and F8. Using electron and scanning microscopy and a new single cell liquid cytotoxic assay, we studied membrane interaction and binding of the CCE fractionated cells with the 2 targets. Effector/target cell conjugates revealed interdigitations in the area of cell contact but no membrane fusion, although certain effector cells had a distinct large granulocytic lymphocyte morphology. Furthermore, different cell types from different fractions were able to bind to the targets although the killing was associated with certain fractions only. When purified monocytes from fraction FF were added to F6 and F8, NK activity against both targets was depressed. This inhibition was not reversed by indomethacin, and binding of the targets to the effector cells was unaffected. CCE is a powerful technique which allows the fractionation of PMNC without altering their biological functions, contrary to what is seen with nylon wool or dextran fractionation. In this report, the activity associated with CCE fractions is studied and discussed.

Antibody-Producing Cells↗
PubMedDate not supplied

Signal transduction in activated natural killer cells and natural killer cells inactivated with sensitive targets.

We have recently demonstrated that the activation of NK cells involves a protein-kinase-C (PKC)-dependent step as well as a phosphatidylinositol (PI)-linked signal transduction system. We have also shown that when NK cells are incubated with sensitive targets for up to 6 h they lose their lytic potential and require IL-2 to regain their lytic activity. PKC is involved in many cell processes such as the transduction of hormonal signals and the machinery of cellular secretion and is activated by diacylglycerol and by a number of phorbol esters, including phorbol myristic acid (PMA). To reinforce the role of PKC in NK-cell-mediated cytotoxicity, we first showed that NK-CMC is inhibited by two agents that inhibit PKC activation, staurosporine and sphingosine. Next, we showed that antibody-dependent cellular cytotoxicity of NK-resistant targets was PKC dependent and Ca2+ dependent. Further, we showed that PMA plus ionophore alone could induce NK killing of resistant targets and that this killing was PKC and Ca2+ dependent. Finally, we contrasted the role of PKC in these activated cells to the role of PKC in cells that have been inactivated with a sensitive target, K562. We showed that PKC is not required for the IL-2-dependent reactivation of NK cells but that Ca2+ is required. To further determine what event in signal transduction is inactivated by K562, we showed that inactivated NK cells do not turnover PI in response to K562 stimulation.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗