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Biomedical subjects

Z Brahmi

Publications and source records attributed to Z Brahmi.

At least 55 records · Page 3Linked to original sources
PubMed1988

Chlorpromazine inhibits human natural killer cell activity and antibody-dependent cell-mediated cytotoxicity.

The phenothiazine antipsychotic drug chlorpromazine, a potent calmodulin antagonist, inhibited human natural killer cell-mediated cytotoxicity in a dose-dependent manner. This inhibition of natural killer cell activity was not due to interference with conjugate formation, nor was it due to toxicity to the natural killer cells or nonspecific alteration of the target cells. Chlorpromazine also suppressed antibody-dependent cell-mediated cytotoxicity in a dose-dependent fashion, suggesting that the two activities share a calmodulin-dependent step. Finally, it was not possible to overcome chlorpromazine-mediated inhibition of natural killer cell activity by first treating the cells with interleukin-2 or Beta-interferon.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1988

Effect of whole-body hyperthermia and cyclophosphamide on natural killer cell activity in murine erythroleukemia.

Mice infected with the polycythemia-inducing strain of Friend virus complex (FVC-P) develop a fatal erythroid disease similar in some respects to leukemia. Six- to eight-week-old DBA/2 female mice were injected i.v. with 0.5 ml of a virus suspension containing approximately 5 X 10(4) plaque-forming units and 5 X 10(3) spleen focus-forming units. Four treatment regimens were begun 3 days postinjection: (a) no treatment; (b) whole-body hyperthermia (WBH) alone; (c) cyclophosphamide (CY) alone; (d) WBH combined with CY. WBH treatment utilized a microwave generator operating at 2450 MHz. The i.p. temperature of the mice receiving WBH was maintained at 39.5-40 degrees C for 30 min. The CY was given i.p. at a dosage of 20 mg/kg of body weight. The various treatments, CY, WBH, CY + WBH were given once a week for 2 weeks. Natural killer cell activity was examined in all four groups of mice and was found to be significantly higher in the animals treated with WBH or CY. Our results show that WBH, either alone or in combination with CY, can prolong the lifespan of mice infected with lethal dosages of the FVC-P, possibly via a mechanism involving natural killer cells.

Animals↗
PubMed1988

Curative effect of split low dosage total-body irradiation on mice infected with the polycythemia-inducing strain of the Friend virus complex.

Split low dose total-body irradiation (TBI) with 150 cGy was assessed for its efficacy in modifying the disease induced in DBA/2 mice by the polycythemia-inducing strain of the Friend virus complex (FVC-P, composed of a Friend murine leukemia helper virus and a spleen focus-forming virus). All FVC-P injected mice were dead within 40 days; however, infected mice receiving TBI on days 5 and 12 exhibited long-term survival. FVC-P-injected mice receiving TBI treatment on days 5 and 12 had normal leukocyte counts, normal spleen weights, and no detectable spleen focus-forming virus. Although the FVC-P-infected mice had decreased proportions of L3T4+ cells and increased proportions of Lyt-2+ cells, these were returned to normal following TBI treatment. Apparently the time sequence of TBI treatments is important since one treatment with TBI on day 5, or two treatments with TBI on days 12 and 18, was not as efficacious. The inability of in vitro irradiation doses of up to 1000 cGy to inactivate FVC-P which was subsequently injected into murine hosts suggests that the effectiveness of the TBI treatment in vivo is not due to a direct radiation effect on the virus. These results indicate a possible relationship between L3T4+ and Lyt-2+ numbers or their ratio in the curative efficacy of TBI in FVC-P-infected mice.

Animals↗
PubMed1988

Phosphatidylinositol metabolism accompanies early activation events in tumor target cell-stimulated human natural killer cells.

This study examined the role of phospholipid metabolism in human natural killer (NK) cells upon activation by tumor target cells(TC). The effector cell (EC) population consisted of peripheral blood lymphocytes enriched for NK cells. Upon a 5-min exposure of EC to the NK-sensitive tumor TC K562 and U937, nearly four- and threefold increases in the incorporation of 32P into phosphatidylinositol (PI) occurred, respectively. In contrast, no increase in 32P incorporation into PI was seen when two NK-resistant TC were used. In addition, little or no change in the incorporation of 32P into phosphatidylcholine, phosphatidylethanolamine, or phosphatidylserine took place with any of the above TC. Depletion of Leu 11b-positive cells abolished the increase in 32P incorporation into PI when K562 were used in the phospholipid assay. Furthermore, labeling kinetics of this phospholipid turnover showed that it occurred less than 5 min following exposure to NK-sensitive TC and that phosphatidic acid, a breakdown product of phosphoinositides, was produced during this 5-min period. These results indicated that metabolism of a phosphoinositide took place and that it occurred in association with early activation events in NK cells. Quercetin and dibutyryladenosine-cyclic monophosphate (dbcAMP) plus theophylline exerted profound inhibitory effects on both NK activity and PI metabolism, suggesting a linkage between the two events. The inhibitors had no effect on target cell-binding capacity, indicating that the inhibition occurred postbinding. PI metabolism took place in the absence of extracellular calcium even though NK activity was completely abolished under the same conditions. Thus, we have shown PI metabolism, but not other phospholipids, to occur in human NK cells upon exposure to NK-sensitive TC, in association with early activation events. This event was independent of extracellular calcium and could be inhibited by quercetin or dbcAMP plus theophylline.

Adult↗
PubMed1988

Target cell directed NK inactivation. Concomitant loss of NK and antibody-dependent cellular cytotoxicity activities.

We investigated the inactivation of human NK cells, a population of large granular lymphocytes (LGL), with K562, an NK-sensitive target cell (TC) and KLCL, an NK-resistant TC, but which can be lysed by NK cells via antibody (Ab)-dependent cellular cytotoxicity. NK-enriched effector cells (ECc) were first treated with either K562 or Ab-coated KLCL (Ab-KLCL). After incubation, ECc were separated from their TC then examined for residual NK and ADCC activities, phenotypic changes, and changes in LGL morphology. K562-treated ECc and Ab-KLCL-treated ECc, when retested against the inactivating TC, respectively, lost greater than 90% of their lytic activities. However, K562-treated ECc lost 60 to 70% of their activity against Ab-KLCL, whereas Ab-KLCL-treated ECc lost less than 10% of their activity against K562. In contrast to what we observed with K562-treated ECc, we detected significant reductions in plasma membrane expression of Leu-11a and Leu-11b on Ab-KLCL-treated ECc. Although the proportion of OKM1+ cells remained unchanged after the inactivation process, the density of OKM1 on both K562-treated ECc and Ab-KLCL-treated ECc increased significantly. Morphologic analysis revealed no apparent differences in the percentages of LGL before and after treatment with K562 or Ab-KLCL. Finally, IL-2 restored lytic potential to both K562-treated ECc and Ab-KLCL-treated ECc and, in addition, IL-2-induced enhancement of Ab-KLCL-treated ECc was accompanied by a partial reexpression of Leu-11a. These data support the hypothesis that NK-cell-mediated cytotoxicity and antibody-dependent cellular cytotoxicity may result from a common lytic mechanism, although the initiation steps and regulation of the pathway are distinct.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1988

Electron spin resonance spectroscopy does not reveal hydroxyl radical production in activated natural killer lymphocytes.

We investigated hydroxyl radical (OH) production by human natural killer (NK) cells, using electron spin resonance (ESR) spectroscopy and 5.5 dimethyl-1-pyrroline-N-oxide (DMPO), a spin trap specific for OH. production. We confirmed that hydroxyl radical scavengers, n-propyl gallate and catechin, inhibited NK cell-mediated cytotoxicity (NK-CMC) in a dose-dependent manner and demonstrated that DMPO also inhibited NK-CMC. Polymorphonuclear leukocytes (PMNL) activated by opsonized zymosan (2.4 mg/ml) and mixed with DMPO (0.14 M) showed an early increase in hydroxyl radical production, leading to a net production of free radical of almost 400 pMol/10(6) cells. We then mixed NK cells with K562, an NK-sensitive tumor cell, at a 1:1 ratio and added DMPO (0.14 M). We pelleted the cells to increase EC to TC binding before taking the sample readings. Activated NK cells showed no increase in OH. production, leading to a net production of free radicals less than 1% that of activated PMNL. These data strongly suggest that hydroxyl radical production does not play a role in the early events of NK cell activation; they indicate a need to reevaluate the mechanism of inhibition of NK-CMC by OH. scavengers.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1988

A comparison of lung metastases and natural killer cell activity in daily fractions and weekly fractions of radiation therapy on murine B16a melanoma.

C57BL/6J male mice were inoculated with 5 X 10(5) B16a melanoma cells. Seven days post-inoculation, when the tumor had grown to 8.0-10.0 mm in diameter, 120 tumor-bearing mice were randomly divided into three groups: (1) sham-irradiated controls, (2) mice receiving 200 cGy five times a week for 6 weeks, and (3) mice receiving 800 cGy once a week for 4 weeks. Thirty mice in each group were sacrificed 47 days postinoculation. Ten mice in each group were observed for the survival time data. The primary tumor was significantly smaller and the number of lung metastases were significantly fewer in mice treated with 800 cGy once a week compared to mice treated with 200 cGy five times a week. When natural killer (NK) cell activity was assessed against YAC-1 tumor targets, it was found to be significantly higher in mice treated with a single large weekly dose of irradiation. These results show that B16a melanoma responds more favorably to a single large dose of irradiation administered once a week compared to the smaller conventional fraction administered five times a week. This beneficial effect correlates with an increase in NK activity, indicating that there may be a causal relationship.

Animals↗
PubMed1987

Whole-body hyperthermia decreases lung metastases in lung tumor-bearing mice, possibly via a mechanism involving natural killer cells.

The effects of whole-body hyperthermia (WBH) on the course of the Lewis lung carcinoma (LLC) and B16 melanoma (B16) were examined. WBH was generated by microwave (2450 MHz) at an intraperitoneal temperature of 39.5-40.0 degrees C and an intratumoral temperature of 40.0-40.5 degrees C for 30 min once a week, X 3 (LLC) or X 6 (B16). The mice were sacrificed 21 days (LLC) or 42 days (B16) after tumor implantation and lung metastases were scored. Natural killer (NK)-cell activity was determined against the YAC-1 tumor target in WBH-treated tumor-bearing mice as well as in tumor-bearing mice but untreated controls. The number of lung metastases was significantly reduced and NK-cell activity was higher in animals treated with WBH. Thus, this study suggests that WBH interferes with the spread of organ metastases, possibly through a mechanism involving NK cells.

Animals↗
PubMed1987

Relevance of soluble cytotoxic factors generated by mycoplasma-contaminated targets to natural killer cell-mediated killing.

The possible involvement of soluble cytotoxic factors (SCF) in the lytic mechanism of natural killer (NK) cell-mediated cytotoxicity (CMC) was investigated. Tumor target cells (TC) were examined for their ability to stimulate the release of SCF from human peripheral blood lymphocytes (PBL). SCF were detected when effector cells (EC) were stimulated with mycoplasma-contaminated (MC)-TC and with concanavalin A (Con A), but mycoplasma-free (MF)-TC were unable to induce SCF. Pretreatment of EC with beta-interferon augmented the production of SCF with MC-K562 and Con A, but not with MF-K562. However, MF-K562 once infected with the culture supernatant from MC-K562, as well as mycoplasmas concentrated from culture supernatant, were able to induce SCF. Only Con A was capable of generating cytotoxic supernatants from EC that had been inactivated with MF-K562 and from EC depleted of Leu 11b positive cells. Moreover, when EC were evaluated for NK activity after coculture with MF-K562, their ability to kill fresh MF-K562 in the standard NK-CMC assay was greatly reduced. This loss of lytic potential was not accompanied by SCF release. Collectively, these data suggest that mycoplasma organisms play a crucial role in the induction of human SCF, and the implication that SCF, including NK cytotoxic factors (NKCF), are the lytic mediators in NK-CMC needs to be re-evaluated.

Adsorption↗
PubMed1986

Role of lipoxygenation in human natural killer cell activation.

Nordihydroguaiaretic acid (NDGA), quercetin, eicosatetraynoic acid (ETYA), phenidone, and esculetin, agents known to inhibit cellular lipoxygenase (LO) activity, also inhibit human natural killer cell-mediated cytotoxicity (NK-CMC) of K562 tumor target cells (TC) in a dose-dependent fashion. Kinetic analysis demonstrated that LO inhibitors blocked an early event in the activation of the lytic mechanism but did not impair conjugate formation. LO inhibitors also did not affect subsequent chromium release, indicating that their site of inhibition was the NK cell and not the TC. The lipoxygenase products 5-hydroperoxyeicosatetraenoic acid (5-HPETE) and leukotriene-B4 significantly enhanced NK activity, with 5-HPETE being the more effective. Other LO products tested included 15-HPETE and the hydroxy derivatives 15-hydroxyeicosatetraenoic acid (15-HETE) and 5-HETE. These LO metabolites were either without effect on NK-CMC or inhibitory, depending upon the concentration. Additionally, we examined the ability of 5-HPETE to circumvent the effects of LO inhibitors and found that, in the presence of NDGA, ETYA or quercetin, 5-HPETE significantly (p less than 0.001) restored lytic activity. Inhibitors of LTB4 and LTC4 synthesis, diethylcarbamazine and U-60,257 respectively, produced no inhibition of NK activity. In fact, U-60,257 significantly (p less than 0.05) enhanced NK-CMC. Previous studies in our laboratory, with a new technique which allows for the separation of NK cells from K562 cells, have shown that K562-treated effector cells are greater than 90% inactivated when retested against fresh K562 in the standard chromium release assay. Lipids were extracted from K562-treated, Percoll-purified LGL and evaluated by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). No significant increases were seen in the arachidonic acid-derived LO products evaluated. Thus, our studies indicate that lipoxygenation may be required in the activation of NK-CMC, possibly as a means to generate oxygen radicals which have been previously implicated in NK-CMC.

Arachidonic Acid↗
PubMed1986

The functional loss of human natural killer cell activity induced by K562 is reversible via an interleukin-2-dependent mechanism.

In a recent study, we evaluated the functional status of human natural killer (NK) cells after their interaction with the NK-sensitive tumor target cell (TC), K562. We demonstrated that effector cells (EC), after treatment with K562 for 4 hr, lost greater than 90% of their original lytic activity. In this investigation, we examined whether this functional loss of NK cell activity represented an irreversible event in the NK lytic mechanism. Initial studies focused on the ability of K562-inactivated EC (ECi), which had been separated from their TC, to recover cytolytic activity following an 18-hr incubation. Our results indicated that ECi recovered 28% of their lytic activity in complete medium (CM) alone, 64% in CM containing interferon-beta (IFN-beta), and 91% in CM supplemented with interleukin 2 (IL-2). Analysis of the data revealed, however, that neither IFN-beta nor IL-2 simply boosted the lytic capacity of NK cells which initially escaped inactivation, but also, each cytokine affected the lytic capabilities of EC that were either truly inactivated by K562 or precursor NK (pre-NK) cells. Thus, to evaluate further the basis of IFN-beta and IL-2-induced ECi augmentation, we first treated the EC with IFN-beta or IL-2 prior to their interaction with K562 so that pre-NK cell subsets would be promoted to fully competent NK cells. Both pretreated EC preparations, after interacting with K562 for 4 hr, lost greater than 90% of their original lytic activities. NK inactivation did not result from cell death nor reflect alterations in conjugate formation or the percentages of Leu-7- and Leu-11-positive EC. IL-2-pretreated ECi, as did ECi, regained some lytic activity after incubation in CM alone, but recovered significantly more activity in CM containing IFN-beta or IL-2. In contrast to the restimulation profiles obtained for ECi and IL-2-pretreated ECi, IFN-pretreated ECi regained lytic function after incubation with IL-2, but not appreciably with IFN-beta or in CM alone. Overall, these findings suggest that EC, either untreated or pretreated with IFN-beta or IL-2, significantly lose their lytic capabilities following interaction with K562 while retaining their ability to bind to the TC; IFN-beta acts predominantly on pre-NK cells, but not on ECi; and IL-2 appears to play an important role in restoring lytic potential to functionally inactive NK cells.

Cells, Cultured↗
PubMed1985

The effect of acute exercise on natural killer-cell activity of trained and sedentary human subjects.

The effect of acute exercise on natural killer (NK) activity and on the distribution of phenotypic characteristics of peripheral blood lymphocytes was examined. Trained and sedentary individuals underwent a standard progressive exercise test on a cycle ergometer using an incremental work load of 15 W (90 kpm), increased every minute. Each subject was encouraged to exercise to exhaustion, and total ventilation and mixed expired O2 and CO2 were measured every 30 sec. All subjects reached the "anaerobic" threshold as judged by the deflection of ventilation at a work load near VO2max. NK activity against K562 reached maximum levels immediately after exercise, dropped to a low point 120 min later, then slowly came back to preexercise levels within 20 hr. No significant differences were observed between the trained and the sedentary groups. Furthermore, immediately after exercise the proportion of OKT-3+ and OKT-4+ cells was reduced by 29.8 +/- 3.6 and 33.6 +/- 5.4%, respectively; the percentage Leu-7+ and Leu-11a+ cells was increased by 53.9 +/- 1.7 and 57.3 +/- 2.9%, respectively. The percentage OKT-8+ cells was not significantly altered. When the percentage binding of effector to target cells was examined, it was highest at 0 min post-exercise (19 +/- 6.2%) and lowest at 120 min postexercise (7 +/- 3.9%), but the absolute number of NK cells remained unchanged. The source of serum used in the lytic assay had no effect on the NK activity, as fetal calf serum and autologous sera drawn at different time intervals during exercise gave similar results.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Evidence for an early calcium-independent event in the activation of the human natural killer cell cytolytic mechanism.

In this study, we examined the functional status of human natural killer (NK) cells after their direct interaction with the NK-sensitive tumor target cell (TC), K562. Human peripheral blood lymphocytes depleted of adherent cells were incubated for 4 hr with unlabeled K562 cells at an effector cell (EC) to TC ratio of 2:1. After incubation, the EC were separated from the TC via centrifugation over a single-step Percoll gradient. K562-treated and separated EC were subsequently shown to be unable to lyse fresh K562 TC when retested in the standard chromium-release assay. Kinetic studies revealed that greater than 90% inactivation of NK cell-mediated cytotoxicity (CMC) could be achieved within 2 hr. Inactivation of NK-CMC by K562 was not caused by a specific loss of NK cells, as detected by changes in the expression of two NK cell-associated markers, Leu-7 and Leu-11, or to alterations in EC viability and target binding cell capacity. Interestingly, NK inactivation also occurred in medium devoid of extracellular calcium, although parallel testing of NK-CMC in the same medium resulted in no chromium release. NK inactivation, however, was significantly prevented when the EC and TC were co-incubated at 4 degrees C, or in medium without magnesium. Additional studies revealed that inactivation of NK-CMC could be achieved with another NK-sensitive, but not with an NK-resistant TC. Overall, we demonstrated that NK cells rapidly lost their lytic potential after direct interaction with a sensitive TC, although the cells remained viable, expressed the same percentage of Leu-7 and Leu-11, and could still bind the TC; and NK inactivation occurred in the absence of extracellular calcium, but not when EC and TC were incubated in medium without magnesium. These latter results provide evidence for an early event in the activation of human NK cells that is binding dependent, temperature sensitive, and independent of extracellular calcium.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1985

Humoral and cellular immune response in ocular histoplasmosis.

We have compared several humoral and cellular immune responses in ocular and in acute histoplasmosis syndromes. T-lymphocyte subset analysis revealed elevated ratios of T-helper/T-suppressor lymphocytes in ten of 22 patients with ocular histoplasmosis, whereas ratios were depressed in 18 of 22 with acute histoplasmosis syndromes. Lymphocyte transformation responses to mitogens and to histoplasma antigens were similar in both acute and ocular histoplasmosis. However, histoplasma antibody levels as measured by immunodiffusion, complement fixation, and radioimmunoassay were elevated in only three of 22 patients with ocular histoplasmosis, compared with 18 of 22 with acute histoplasmosis. Natural killer cell cytotoxicity was depressed in ten of 20 patients with ocular histoplasmosis compared with none of 18 with acute histoplasmosis. These findings support the clinical observations that ocular histoplasmosis and acute histoplasmosis syndrome are seldom, if ever, seen in the same patient.

Antibodies, Fungal↗
PubMed1984

Changes in immunoregulatory lymphocyte populations in patients with histoplasmosis.

Circulating T-lymphocyte subpopulations were enumerated in 65 patients with histoplasmosis and correlated with the different clinical manifestations of the disease. Acute pulmonary histoplasmosis, rheumatologic, disseminated, and chronic inflammatory manifestations of histoplasmosis were all associated with a significant elevation above normal of OKT8+ (suppressor-cytotoxic) lymphocytes and a significantly lower than normal OKT4+ (helper-inducer)-lymphocyte to OKT8+-lymphocyte ratio. In contrast, cavitary disease was associated with an increase in OKT4+ lymphocytes, a decrease in OKT8+ lymphocytes, and a higher than normal OKT4/OKT8 ratio. Clinical recovery was associated with normalization of these values. Functional activity determined by coculture techniques correlated closely with T-lymphocyte subset measurements. These distinct subset abnormalities may help monitor immunological aspects of disease activity.

Antibodies, Monoclonal↗
PubMed1984

Monoclonal antibody against K562 cell line accelerates killing of the target cells by large granular lymphocytes.

A monoclonal antibody (MoAb 11-4) was raised against K562, a human erythroleukemia cell line sensitive to natural killer cell-mediated cytotoxicity (NK-CMC). Immunological analysis revealed MoAb to be IgG2b. Alone, the MoAb was not cytotoxic for K562 and did not bind to the effector cells, but the addition of this antibody to macrophage-depleted human peripheral blood lymphocytes increased killing of K562 in a 4-hr NK-CMC assay. The maximum increase in NK-CMC was observed when MoAb 11-4 was added to target cells prior to the formation of effector/target cell conjugates. This effect was dose dependent, was specific for K562, and, contrary to conventional antisera, occurred at very low concentrations of MoAb. When MoAb was added either to Percoll-purified large granular lymphocytes (LGL) or to LGL-depleted lymphocytes, only the latter demonstrated a significant increase in the killing of K562 in a 4-hr chromium release assay. Kinetics studies revealed that although the overall LGL-mediated lysis was only slightly increased at 4 hr, the maximum lytic activity was reached within 2 hr. These studies suggest that (1) human LGL and LGL-depleted cell populations bear Fc receptors for mouse IgG2b and (2) although the cytotoxic activities of both cell populations are increased by treatment with MoAb 11-4, the kinetics of this increase are different.

Animals↗