Effect of glutamine on Th1 and Th2 cytokine responses of human peripheral blood mononuclear cells

Decreased glutamine concentrations are found in patients with catabolic stress and are related to susceptibility to infections. In this study, we evaluated the role of glutamine in Th1/Th2 cytokine responses. Peripheral blood mononuclear cells were stimulated with phytohemagglutinin (PHA), live attenuated bacillus Calmette-Guérin (BCG), or measles virus in the presence of different glutamine concentrations. We found that glutamine at an optimal concentration (0.6 mM) significantly enhanced PHA-stimulated lymphocyte proliferation as well as Th1 [interferon-gamma (IFN-gamma) and interleukin-2 (IL-2)] and Th2 cytokine (IL-4 and IL-10) production. In the absence of glutamine, BCG and measles virus elicited minimal lymphocyte proliferation, whereas BCG enhanced Th1 cytokine response and measles virus promoted Th2 cytokine response. Interestingly, addition of glutamine promoted the BCG-elicited Th1 cytokine response (IFN-gamma), but suppressed the measles-induced Th2 cytokine response (IL-10). These results suggest that appropriate glutamine levels may influence host responses to different antigens and microorganisms. Furthermore, predominately Th1, but not Th2, cytokine responses required the presence of optimal concentrations of glutamine.

Lymphocyte proliferation modulated by glutamine: involved in the endogenous redox reaction

Decreased glutamine concentrations are found during catabolic stress and are related to susceptibility to infections. However, little is known about the mechanism of glutamine modulation of lymphocyte functions. Glutamine is not only an important energy source in mitochondria, but is also a precursor of glutamate, which is used for cellular glutathione (GSH) biosynthesis in lymphocytes. In this study, we investigated the effects of glutamine on the redox reaction during lymphocyte proliferation. Peripheral blood mononuclear cells, obtained from healthy adult volunteers, were cultured and stimulated by phytohaemagglutinin (PHA) in the presence of different glutamine concentrations. Cells were harvested and prepared for analysis of lymphocyte proliferation, cell cycle propagation, intracellular glutathione levels and reactive oxygen species (ROS) production. We found that glutamine supplementation significantly enhanced PHA-stimulated lymphocyte proliferation and propagation of the cell cycle from the G1 to S and G2/M phases. Glutamine also enhanced production of both intracellular ROS and GSH levels in PHA-stimulated lymphocytes. Flow cytometric analysis by the mercury orange staining method showed that glutamine significantly enhanced intracellular non-protein thiols in PHA-stimulated CD4+, but not CD8+ lymphocyte subsets. Furthermore, intracellular GSH detected by monochlorobimane dye probe showed that glutamine enhanced GSH both in PHA-stimulated CD4+ and CD8+ lymphocyte subsets. Inadequate glutamine supplementation resulted in decreased lymphocyte proliferation in association with decreased levels of intracellular GSH. Addition of exogenous GSH significantly enhanced lymphocyte proliferation, whereas blockade of GSH synthesis enhanced ROS production and suppressed lymphocyte proliferation. These results suggest that the modulation of PHA-stimulated lymphocyte proliferation by glutamine is closely related to the maintenance of appropriate intracellular redox status.

Leukocyte adhesion deficiency disorder: report of one case

In this paper, a case of leukocyte adhesion deficiency disorder confirmed by flow cytometry and leukocyte chemotaxis assays is reported. The 32-day-old female infant was admitted to our ward on account of delayed umbilical cord detachment and omphalitis. After admission, hemogram revealed severe leukocytosis (white blood cell (WBC) counts: 86,800/cumm), and there was poor clinical response to several kinds of antibiotics. The above history indicated that the patient might be a case of leukocyte adhesion deficiency disorder. A definite absence of CD11b/CD18 adhesion molecule on the patient's granulocytes and severe defects of leukocyte function demonstrated by chemotaxis, chemokinesis and zymosan-induced respiratory burst assays confirmed this diagnosis.

Hypokalemia and salbutamol therapy in asthma

Hypokalemia is a common side effect in adult asthmatic patients on beta 2 adrenergic therapy. There is limited information in regard to hypokalemia and its relation to the clinical responses following administration of beta 2 agonist therapy in children with asthma. We observed that salbutamol inhalation significantly improved asthmatic symptoms as demonstrated by increases in peak expiratory flow (PEF: 122.37+/-75.38 vs. 152.59+/-80.29; P < 0.001) and venous oxygen tension (Pv,O2: 33.24+/-4.95 vs. 58.16+/-2.31; P < 0.001), and decreases in respiratory rate (RR: 36.39+/-3.78 vs. 28.62+/-3.12; P< 0.01), clinical scores (CS: 3.59+/-1.28 vs. 1.59+/-0.71), and venous PCO2 tensions (Pv,CO2: 40.84+/-2.67 vs. 34.75+/-2.31; P < 0.001). Salbutamol-induced hypokalemia was correlated with a decrease in RR, and an increase of Pv,O2 and PEF. These findings suggest that the same mechanism is involved in eliciting hypokalemia and bronchodilatation.

Application of chromosome 4q35-qter marker (pFR-1) for DNA rearrangement of facioscapulohumeral muscular dystrophy patients in Taiwan

Facioscapulohumeral muscular dystrophy (FSHD) has been found to be linked to chromosome 4qter. A chromosome 4q35-ter marker, pFR-1 (subclone of the cosmid c51), has been recently isolated and used as a probe for mapping near, or within, the FSHD gene. To examine FSHD-associated DNA rearrangements in the Taiwan population, we used the pFR-1 probe to perform Southern blot analysis on 142 individuals, including 32 FSHD patients within 9 autosomal dominant families, five sporadic FSHD patients from 4 families (include one pair of twins), three sporadic scapuloperoneal syndrome (SPS) patients and two sporadic polymyositis patients with their unaffected parents, and 29 healthy controls. In 29 healthy individuals, 3 SPS and 2 polymyositis patients with their families, probe pFR-1 analysis revealed that all had polymorphic restriction fragments that were larger than 28 kb in length. All but 1 FSHD-affected individual had specific smaller EcoRI fragments (ranging in size from 10.5 to 27 kb). Two point linkage analysis between pFR-1 and the FSHD locus provided significant evidence for FSHD linkage (Z(max)=6.84). A similar smaller fragment was also present in 5 sporadic patients, while this smaller fragment could not be found in one of their parents. Identical EcoRI restriction fragment length polymorphism (RFLP) patterns linked to FSHD were shown in the monozygotic twins, even though they showed extreme variability in the expression of FSHD. We conclude that the pFR-1 probe is a tightly linked marker of FSHD and can be used to detect most DNA rearrangements associated with this disease in the Taiwan population. However, the same RFLP patterns may represent extreme variability in the expression of the FSHD gene.

When do human macrophages release nitric oxide? Variable effects of certain in vitro cultural and in vivo resident conditions

Nitric oxide (NO) release from mouse and rat macrophages is implicated in tumor cell cytotoxicity and the killing of intracellular organisms. Evidence, however, suggests that human monocyte-derived macrophages or myeloid leukemic cells differentiated along the monocytic lineage do not consistently release NO. Results presented herein that human monocyte-derived macrophages in response to lipopolysaccharide can release NO, but markedly less than mouse macrophages (1.26 +/- 0.20 vs 42.5 +/- 6.3 microM). Different in vitro and in vivo conditions have variable effects on NO production by human macrophages. Monocytes cultured in plastic wells, but not teflon beakers, for 7 days can release NO (1.22 +/- 0.13 vs 0.14 +/- 0.07 microM). In addition, human resident macrophages derived from patients with certain diseases possess a calcium- and protein kinase C-dependent pathway to produce NO, in contrast to the calcium-independent and phosphatase-dependent NO release in murine macrophages. Above results suggest that the mechanism of producing NO by macrophages in humans is not only different from that in mice, but also depends on certain in vitro and in vivo conditions.

Generation of interleukin-8 from human monocytes in response to Trichomonas vaginalis stimulation

Neutrophils are the predominant inflammatory cells found in the vaginal discharges of patients with Trichomonas vaginalis infection. We have investigated the possible role of interleukin-8 (IL-8) in the inflammatory response elicited by T. vaginalis infection. This study has shown that T. vaginalis induces blood monocytes to produce large amounts of bioactive IL-8, mainly by membrane components of T. vaginalis (MTV). Monocyte-derived IL-8 induced by MTV was dose and time dependent. The peak level of IL-8 was 102 +/- 11 ng/ml of conditioned media (mean +/- standard error; n = 5) obtained from MTV-stimulated monocytes (MTVCM) at 36 h of cultivation. With a multichamber chemotactic assay, we found an optimal neutrophil chemotaxis (177 +/- 14 migrated cells) induced by MTVCM collected at 16 h of cultivation when the level of IL-8 was 42 +/- 8 ng/ml. A neutralizing monoclonal antibody directed against IL-8, but not the irrelevant antibodies, significantly blocked the neutrophil chemotactic activity (decreased from 153 +/- 6 to 23 +/- 3 migrated cells; n = 3 [P < 0.001]) induced by MTVCM. Moreover, the maximum increase of the IL-8 mRNA level from MTV-treated monocytes was observed after a 5-h cultivation and decreased thereafter. Monocytes cocultured with MTV in the presence of a neutralizing monoclonal antibody directed against tumor necrosis factor alpha, but not against IL-1 beta, decreased IL-8 production by 25% (P < 0.05), indicating that the release of IL-8 in MTV-stimulated monocytes is partially dependent on tumor necrosis factor alpha. The capacity of MTV-induced monocytes to synthesize IL-8 suggests that these cells can contribute to the induction of the acute inflammatory response seen in T. vaginalis infection.

Cytotoxic factors released by dengue virus-infected human blood monocytes

Human monocyte-derived cytotoxic factors (CF) induced by dengue virus were studied. Using several human leukemia cell lines as precursors, the biological activities of CF in conditioned medium from dengue virus-infected monocytes were demonstrated through the measurement of tumor cell growth inhibition. The conditioned medium from dengue virus infected monocytes suppressed significantly growth of CEM, HL60, K562, and U937 cells. In the presence of 10% conditioned medium (v/v) from dengue virus infected monocytes, DNA synthesis of U937 cells, as measured by [3H]thymidine incorporation, decreased by 99% in contrast to their synthesis in conditioned medium from noninfected control monocytes, which did not have any suppressive effect. Partial characterization of CF showed that it is a proteinase-K-sensitive and heat-labile protein with a molecular mass over 100 kDa. Employing a flow cytometric analysis of the cell cycle, it was found that U937 cells, treated either with conditioned medium from dengue virus infected monocytes or with CF, but not treated with conditioned medium from noninfected monocytes, showed cell-cycle arrest in G1 phase by 48 hr. This suppressive effect of CF on U937 growth was dose- and time-dependent. These results suggest that dengue virus-infected monocytes may produce CF to target myeloid cells, resulting in the hematological changes observed in patients with dengue fever.

Pentoxifylline augments but does not antagonize TNF alpha-mediated neuroblastoma cell differentiation: modulation of calcium mobilization but not cAMP

We described here that pentoxifylline (PTX), which is well known to counteract tumor necrosis factor alpha (TNF alpha)-mediated inflammatory responses, augmented TNF alpha-induced neuroblastoma cell differentiation in conjunction with growth inhibition and cell-cycle arrest in G1 phase. PTX also enhanced TNF alpha-induced down-regulation of acetylcholine-mediated [Ca2+]i mobilization in neuroblastoma cells. Furthermore, we found that addition of cAMP failed to induce neuroblastoma cell differentiation, whereas blockade of [Ca2+]i mobilization by 8-(N,N-diethyl-amino)octyl-3,4,5-trimethoxybenzoate HCl (TMB-8, 10 microM) did induce neuroblastoma cell differentiation. Taken together, these results indicated that PTX possessed a novel signal transduction, down-regulation of [Ca2+]i mobilization, to augment but not counteract TNF alpha-mediated functions.

A model to study cytokine profiles in primary and heterologously secondary Dengue-2 virus infections

Roles of cytokines in primary and secondary Dengue virus (DV) infections are not completely understood. In this study, we challenged mononuclear leukocytes (MNLs) obtained from non-immune and DV-1-infected donors with DV-2 in vitro to mimic primary and heterologously secondary DV-2 infections, respectively. We found that MNLs in response to DV-2 could release a large amount of interleukin-1 (IL-1 beta) and tumor necrosis factor alpha (TNF alpha). However, IL-1 beta and TNF alpha released by MNLs with primary or heterologously secondary exposure to DV-2 were not significantly different. In contrast, MNLs with heterologously secondary DV-2 infections produced significantly higher amount of interferon gamma (IFN gamma) than those with primary DV-2 infections. These results suggest that IFN gamma, but not TNF alpha or IL-1 beta, may in part participate in the pathogenesis of Dengue shock syndrome (DSS) frequently found in heterologously secondary DV-2 infections.

Hydroxyl radicals as an early signal involved in phorbol ester-induced monocytic differentiation of HL60 cells

A useful model for the study of monocytic differentiation has been the induction of myeloid leukemic cell differentiation. Employing human HL60 leukemic cells, we sought to clarify whether reactive oxygen intermediates (ROI) are involved in phorbol myristate acetate (PMA)-induced monocytic differentiation. We found that hydroxyl radical (OH.) scavenger pyrrolinodimethylthiocarbamate (PDTC), but not O2-, H2O2 or 1O2 scavenger, suppressed PMA-mediated HL60 cell differentiation in a dose dependent fashion (0.1 to 1.0 microM). PDTC suppressed OH. but not O2- or H2O2 production by HL60 cells stimulated with PMA (32 nM). Addition of PDTC before and right after, but not 16 hours after, PMA stimulation inhibited PMA-induced HL60 cell differentiation. Taken together, these findings indicate that OH., but not O2-, H2O2, or 1O2, is a critical early signal involved in the PMA-induced monocytic differentiation of HL60 cells.

Neuroblastoma cell-mediated leukocyte chemotaxis: lineage-specific differentiation of interleukin-8 expression

To determine whether neural crest-derived neuroblastoma cells may release cytokines which regulate the function of leukocytes, we found that neuroblastoma (HTB-11) cells did not constitutionally express IL-1 beta, TNF alpha, or IL-8 mRNA. However, TNF alpha, which induced HTB-11 cells to differentiate to perineurium-like cells, induced expression of IL-8 mRNA in a dose- and time-dependent fashion. In contrast, pentoxifylline (1 mM), which promoted HTB-11 cells to differentiate to polygonal neuron-like cells, did not induce IL-8 mRNA expression. As determined by enzyme-linked immunoassay, high levels of IL-8 were detectable in the culture supernatants from TNF alpha-treated neuroblastoma cells, but not pentoxifylline-treated neuroblastoma cells (19.60 +/- 2.34 vs 0.10 +/- 0.06 ng/ml). Culture supernatants obtained from TNF alpha-treated neuroblastoma cells induced chemotaxis of neutrophils and lymphocytes that was significantly blocked by anti-IL-8 neutralizing antibodies. Detection of a leukocyte chemotactic factor was not observed in the culture supernatants from pentoxifylline-treated cells. These results suggest that neural crest-derived perineurium-like cells, but not neuron-like cells, may release a leukocyte chemotactic factor or factors such as IL-8 which could be involved in leukocyte recruitment seen in inflammatory diseases affecting peripheral nerves.

Effects of fibronectin on actin organization and respiratory burst activity in neutrophils, monocytes, and macrophages

Previous studies have shown that fibronectin (Fn) enhances phagocytosis and killing of antibody-coated bacteria by neutrophils and macrophages. In an attempt to understand the mechanism of this enhancement, we have investigated the effects of Fn on phagocytosis-related actin organization as well as respiratory burst activity in neutrophils, monocytes and culture-derived macrophages. Employing an NBD-phallacidin flow cytometric analysis of filamentous actin formation, we found that Fn promotes rapid actin polymerization within 30 seconds in neutrophils, monocytes, and macrophages, but not lymphocytes. Enhancement of actin polymerization by Fn was concentration-dependent and mediated by a pertussis toxin- but not cholera toxin-sensitive G protein. Inhibition of protein kinase C by sphingosine (20 microM), calcium influx by verapamil (0.1 mM), or intracellular calcium mobilization by 8-(N,N-diethyl-amino) octyl-3,4,5-trimethoxybenzoate HCl (TMB-8; 0.1 mM) did not block Fn-enhanced actin polymerization in phagocytes. Incubation of neutrophils and macrophages on microtiter plates precoated with Fn suppressed superoxide (O2-) production induced by IgG- and IgA- opsonized group B streptococci. In contrast, Fn significantly enhanced IgA- and IgG-mediated O2- production by freshly isolated monocytes. These data suggest that Fn enhances phagocytosis, presumably through G protein-coupled cytoskeleton reorganization and augments O2- production by circulating monocytes. In contrast, it appears to suppress O2- production by the active phagocytic cells, neutrophils and macrophages. This may result in enhanced phagocytosis and intracellular killing of microorganisms without damaging interstitial tissues.

All-trans retinoic acid reverses phorbol ester resistance in a human myeloid leukemia cell line

Treatment of human HL-60 leukemic cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) is associated with activation of protein kinase C (PKC) and induction of monocytic differentiation. An HL-60 variant cell line, termed HL-525, derived from long-term exposure to TPA (Homma et al, Proc Natl Acad Sci USA 83: 7316, 1986) is resistant to TPA-induced differentiation and displays decreased PKC beta expression compared with the HL-60 parent line. However, this variant exhibits features of granulocytic differentiation, including nitroblue tetrazolium reduction, when exposed to all-trans retinoic acid (ATRA). Whereas treatment of HL-525 cells with ATRA or TPA alone had no effect on features of monocytic differentiation, these agents in combination resulted in cellular adhesion, nonspecific esterase staining, and induction of the c-fms (monocyte growth factor receptor) gene. In order to measure PKC expression associated with the reversal of TPA resistance by ATRA, we exposed HL-525 cells to ATRA and analyzed PKC-mRNA and protein levels. Exposure of HL-525 cells to ATRA for 3 days resulted in induction of PKC beta transcripts, whereas there was little change in PKC alpha mRNA levels. ATRA treatment was also associated with an increase in PKC activity and an induction of cytosolic PKC beta protein levels. These findings are consistent with the hypothesis that ATRA reverses TPA resistance in HL-525 cells by enhancing the expression of PKC.

Induction of interleukin-8 expression in neuroblastoma cells by retinoic acid: implication of leukocyte chemotaxis and activation

Neuroblastoma cells in response to retinoic acid (RA) exhibit differentiation. RA, which can promote tumor cell differentiation, has also been shown to regulate tumor-infiltrating leukocytes. In an attempt to explore the relationship between RA-induced neuroblastoma cell differentiation and leukocyte chemotaxis, we investigated expression of IL-1 beta, IL-8, granulocyte-macrophage colony stimulating factor, and tumor necrosis factor-alpha in the undifferentiated and RA-induced differentiated neuroblastoma cells. Using SK-N-SH neuroblastoma cells, we found that RA induced differentiation of SK-N-SH cells as demonstrated by down-regulation of N-myc gene expression, cell-cycle arrest in G1 phase, and phenotypic change. Neither RA-treated nor untreated neuroblastoma cells expressed IL-1 beta, granulocyte-macrophage colony stimulating factor, or tumor necrosis factor-alpha mRNA. RA-treated but not untreated SK-N-SH cells expressed IL-8 mRNA in a time- and dose-dependent fashion. As determined by ELISA, IL-8 levels were detectable in the culture supernatants from RA-treated, but not untreated, neuroblastoma cells (2.65 +/- 0.43 versus 0.05 +/- 0.04 ng/mL). Using neutrophil and lymphocyte chemotactic assays, we found that RA-treated but not untreated culture supernatants of neuroblastoma cells promoted neutrophil and lymphocyte chemotaxis. The RA enhancement of neuroblastoma cell-mediated leukocyte chemotaxis was significantly blocked by anti-IL-8 neutralizing antibodies. These results suggest that RA-induced neuroblastoma cell differentiation is associated with production of functional IL-8, which may be involved in the leukocyte infiltration and activation resulting in tumor regression.

A novel neutrophil-activating factor released by Trichomonas vaginalis

We have investigated the effects of a novel neutrophil-activating factor released by Trichomonas vaginalis (TV-NAF) on neutrophil chemotaxis. TV-NAF was present in the supernatant from 10(7) T. vaginalis (STV) cultured in 1 ml of serum-free Hanks' balanced salt solution (HBSS) at 37 degrees C for 30 min. With a multichamber chemotactic assay, we found that there were 112 +/- 15 migrated neutrophils (mean +/- standard deviation, n = 7) for STV and 11 +/- 4 for HBSS per high-power field (x 400). STV was also able to induce neutrophil actin assembly (increased 1.5-fold), enhance expression of complement receptor type 3 (increased 5-fold), and promote intracellular calcium mobilization (increased 2.5-fold). There was no chemotactic activity in the preparation of STV from killed trichomonads. The fact that heating up to 100 degrees C or deproteinization by treatment with proteinase K at 65 degrees C for 1 h did not abolish its chemotactic activity suggests that the TV-NAF involved was not a protein. The chemotactic activity of TV-NAF was associated with the fraction containing small molecules of less than 3,000 Da. Therefore, the possibility that eicosanoid production by trichomonads is responsible for neutrophil activation was investigated. Leukotriene B4 (LTB4; 500 pg/ml) but not thromboxane B2 (< 20 pg/ml) or prostaglandin E2 (< 8 pg/ml) was found in the STV by radioimmunoassay. Production of LTB4 by trichomonads was time dependent and increased twofold when arachidonic acid (100 microM) was added but was not decreased when eicosanoid inhibitors were present. Evidence for the presence of LTB4 in STV was further provided by the fact that rabbit anti-LTB4 antiserum could abolish the chemotactic activity of STV. These studies suggest that the spontaneous release of TV-NAF, which is most likely LTB4, may activate neutrophils, presumably through a different arachidonate metabolic pathway than that in mammalian cells.

Effects of phenobarbital on leukocyte activation: membrane potential, actin polymerization, chemotaxis, respiratory burst, cytokine production, and lymphocyte proliferation

Leukocyte activation is known to involve cell membrane potential changes. Phenobarbital, an anesthetic and anticonvulsant that can inhibit neuronal membrane depolarization, may also affect leukocyte activation. Measuring membrane potential, actin polymerization, chemotaxis, superoxide production, lymphocyte proliferation, intracellular calcium concentration, and cytokine production, we found that phenobarbital at a concentration of 15-30 micrograms/ml, which is considered a therapeutic serum level for controlling seizures, did not affect polymorphonuclear neutrophil (PMN) activation. At levels higher than 100 micrograms/ml, phenobarbital significantly suppressed formylmethionyl-leucyl-phenylalanine (fMLP)-induced chemotaxis. Concentrations greater than 300 micrograms/ml also inhibited phorbol myristate acetate-stimulated membrane potential change. In contrast, 30 micrograms/ml phenobarbital significantly inhibited lymphocyte proliferation stimulated by phytohemagglutinin (PHA) and pokeweed mitogen. This concentration of phenobarbital also suppressed the increase of intracellular free calcium induced by PHA. However, only a higher concentration of phenobarbital (300 micrograms/ml) was able to inhibit PHA-induced interleukin-2 (IL-2) production and suppress the proliferation of PHA-induced IL-2 receptor-bearing lymphocytes. These results suggest that concentrations of phenobarbital associated with anticonvulsive levels do not affect PMN activation but suppress lymphocyte activation, possibly by affecting intracellular signal transduction.

Effect of picibanil (OK432) on neutrophil-mediated antitumor activity: implication of monocyte-derived neutrophil-activating factors

Picibanil (OK432), an extract from streptococci, has been widely utilized to treat malignant ascites and pleural effusions. The antitumor mechanism is believed to include complement-mediated neutrophil activation. Employing a flow-cytometric analysis of actin polymerization as an indicator of cell activation as well as a tumor proliferation assay, we have found that monocyte-derived neutrophil-activating factors were involved in OK432-induced neutrophil activation as well as antitumor activity. OK432-stimulated (0.1 KE/ml; 0.01 mg/ml) monocyte supernatants (OKMS) induced neutrophil actin polymerization and chemotaxis. OKMS were responsible for neutrophil-mediated inhibition of human leukemic (CEM) cell proliferation and stimulated neutrophils to produce superoxide in the presence of CEM leukemic cells at an effector/target ratio higher than 20/1. In contrast, OK432 alone, OK432-stimulated lymphocyte supernatants, or OK432-stimulated neutrophil supernatants had no effect on neutrophil activation or suppression of tumor cell proliferation. OK432 in combination with mononuclear cells also had no effect on the inhibition of CEM cell proliferation. Pretreatment of OKMS at 56 degrees C for 30 min did not affect its ability to activate neutrophils, implying that complement activation is not responsible for the neutrophil activation. Supernatants from OK432-stimulated mononuclear cells, as determined by enzyme-linked immunosorbent assays and radioimmunoassays, contained high levels of interleukin-8 (IL-8; 1567 +/- 145 pg/ml) and tumor necrosis factor (TNF alpha; 2105 +/- 152 pg/ml), low levels of leukotriene B4 (800 +/- 45 pg/ml) and IL-1 beta (180 +/- 22 pg/ml), but interferon gamma was not detectable. IL-1 beta, IL-8, and TNF alpha transcripts, undetectable in untreated monocytes, increased significantly after 30-60 min exposure to OK432. These results suggest that neutrophil-activating factors from monocytes or resident macrophages may play an important role in the OK432-induced neutrophil activation and antitumor activity.

Immunoglobulin G-dependent classical complement pathway activation in neutrophil-mediated cytotoxicity to infective larvae of Angiostrongylus cantonensis

The participation of antibody and complement in cell-mediated adherence and cytotoxicity to infected larvae (L3) of Angiostrongylus cantonensis was investigated in vitro. Of the different cell types involved in the reaction, neutrophils were seen to have a predominant role in immune serum--dependent adherence and cytotoxicity to L3. In the presence of immune serum, cytotoxicity to L3 by neutrophils from infected rats was twice that of neutrophils from normal rats. Although mononuclear cells and eosinophils from infected rats significantly increased the adherence to L3, they had little lethal effect on L3. A further study using gel filtration (Sephacryl S-200) and affinity chromatography (protein A) revealed that immunoglobulin G (IgG) alone was responsible for the complement activation in neutrophil-mediated killing of L3. Neither adherence nor cytotoxicity to L3 by neutrophils were affected when immune serum was heated to 50 degrees C or treated with zymosan, but they were markedly decreased when immune serum was treated with Mg2(+)-ethylene glycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. The results of this study indicate that the neutrophil-mediated adherence and cytotoxicity to L3 of A. cantonensis are mediated through IgG-dependent classical complement pathway activation.

Effect of fibronectin on IgA-mediated uptake of type III group B streptococci by phagocytes

Previous studies have shown that a type-specific IgA monoclonal antibody alone or in combination with fibronectin (Fn) enhances protective efficacy in two animal models of group B streptococcal infection. To investigate the mechanisms by which IgA mediates protection, the effects of Fn on phagocytosis of group B streptococci (GBS) opsonized with a type III-specific IgA monoclonal antibody were examined. Specific IgA alone or in combination with Fn did not promote the phagocytosis of GBS by polymorphonuclear leukocytes (PMNL). Fibronectin also had no significant effect on phagocytosis of IgA-opsonized GBS by monocytes. Specific IgA alone promoted phagocytosis of GBS by culture-derived macrophages in a dose-dependent fashion. Fibronectin enhanced macrophage uptake of the GBS opsonized in a suboptimal concentration of specific IgA (phagocytic index = 2.32 +/- 0.56 vs. 3.26 +/- 0.48 with Fn; P less than .05). These data suggest that protection against GBS in neonatal rats by a combination of Fn and specific IgA is mediated by macrophages rather than by PMNL or monocytes. Fibronectin may have a critical role in host defense at sites where IgA and macrophages predominate.

An IgA monoclonal antibody directed against type III antigen on group B streptococci acts as an opsonin

We have investigated the mechanisms by which a murine IgA mAb directed against the type III Ag (IgA anti-III mAb) of group B streptococci (GBS) protects neonatal rats from lethal infection with these organisms. Purified IgA anti-III mAb enhanced phagocytosis of type III GBS by rat peritoneal macrophages in vitro by fourfold compared with phagocytosis of buffer-treated GBS. In the absence of antibody, neonatal rat serum did not promote phagocytosis, but addition of neonatal rat serum to GBS opsonized with IgA anti-III led to a sevenfold increase in phagocytosis. Heat inactivation of C destroyed the ability of neonatal rat serum to enhance phagocytosis in the presence of IgA. C3 deposition was observed when GBS coated with IgA anti-III mAb were incubated in untreated neonatal rat serum or in serum treated with Mg/EGTA. This latter observation suggested that C3 deposition occurred through activation of the alternative pathway. The control IgA mAb MOPC 315 did not enhance GBS ingestion or C3 deposition on GBS. Depletion of C in vivo by using cobra venom factor abolished the protective effect of IgA anti-III mAb in the neonatal rat model. These data suggest that the ability of this IgA to activate C further enhances its opsonic activity and may be essential for its protective effect in vivo.

An IgA monoclonal antibody directed against type III antigen on group B streptococci acts as an opsonin

We have investigated the mechanisms by which a murine IgA mAb directed against the type III Ag (IgA anti-III mAb) of group B streptococci (GBS) protects neonatal rats from lethal infection with these organisms. Purified IgA anti-III mAb enhanced phagocytosis of type III GBS by rat peritoneal macrophages in vitro by fourfold compared with phagocytosis of buffer-treated GBS. In the absence of antibody, neonatal rat serum did not promote phagocytosis, but addition of neonatal rat serum to GBS opsonized with IgA anti-III led to a sevenfold increase in phagocytosis. Heat inactivation of C destroyed the ability of neonatal rat serum to enhance phagocytosis in the presence of IgA. C3 deposition was observed when GBS coated with IgA anti-III mAb were incubated in untreated neonatal rat serum or in serum treated with Mg/EGTA. This latter observation suggested that C3 deposition occurred through activation of the alternative pathway. The control IgA mAb MOPC 315 did not enhance GBS ingestion or C3 deposition on GBS. Depletion of C in vivo by using cobra venom factor abolished the protective effect of IgA anti-III mAb in the neonatal rat model. These data suggest that the ability of this IgA to activate C further enhances its opsonic activity and may be essential for its protective effect in vivo.

Effect of pentoxifylline on developmental changes in neutrophil cell surface mobility and membrane fluidity

Polymorphonuclear leukocytes (PMNs) from human neonates respond less efficiently to chemotactic factor stimulation than do PMNs from adults. The biologic mechanisms underlying this developmental process are poorly understood. In previous studies, we have found that pentoxifylline, an agent report to enhance membrane deformability, increased the chemotactic response of neonatal PMNs. In the present studies, we have examined the effect of pentoxifylline on cell surface mobility and membrane fluidity by assessing fluorescent concanavalin A (Con A) capping and fluorescent polarization (FP). Baseline Con A capping was lower in the PMNs of neonates when compared to PMNs from adult controls. Colchicine, which increases capping by disrupting microtubules, exaggerated the differences between the adult and neonatal PMNs. Following exposure of neonatal PMNs to pentoxifylline, colchicine enhanced Con A capping to levels equivalent to those of colchicine-treated PMNs from adults. Employing a fluorescence polarization (FP) assay, we found the fluid state of the membrane of PMNs from neonates was significantly less than that of adult controls. Pentoxifylline alone significantly increased the fluidity of the cell membranes of neonatal PMNs while decreasing elevated basal levels of F-actin in the cell. These data suggest an intrinsic cytoskeletal difference in the PMNs of neonates that may be responsive to pharmacologic manipulation.

Effect of immune globulin intravenous on opsonization of bacteria by classic and alternative complement pathways in premature serum

The mechanisms involved in the effect of immune globulin intravenous (IGIV) on bacterial opsonization by both complement pathways in premature serum were elucidated in this study. Of the bacteria used, Staphylococcus aureus and Salmonella enteritidis were nonencapsulated while Streptococcus pyogenes and Escherichia coli 07 K1 were encapsulated. As demonstrated by indirect immunofluorescence, IGIV showed specific antibody titers of 1:32 for S. aureus and S. enteritidis and of 1:8 for S. pyogenes and E. coli 07 K1. IGIV alone had no direct opsonic activity against these organisms. Addition of IGIV did not alter the opsonic activity of normal adult serum against these organisms. In contrast, addition of IGIV promoted the opsonic activity of premature serum against the nonencapsulated bacteria to levels matching that in normal adult serum. The IGIV preparation significantly improved the opsonization of bacteria by the classic (from 39 to 68% of that in adult serum) and alternative (from 22 to 97% of that in adult serum) complement pathways in premature serum. IGIV also markedly augmented C3 deposition on the bacteria by both complement pathways. These studies suggest that IGIV containing high titers of specific antibodies promote opsonization of bacteria by the enhancement of complement pathway activation, especially the alternative pathway, in premature serum.

Mechanisms of bacterial opsonization by immune globulin intravenous: correlation of complement consumption with opsonic activity and protective efficacy

To study the mechanism of bacterial opsonization by immune globulin intravenous (IGIV) complement consumption and polymorphonuclear leukocyte (PMNL) membrane receptor (FcRlo, CR1, and CR3)-mediated phagocytosis of Staphylococcus epidermidis, Klebsiella pneumoniae, and groups A and B streptococci were examined. IGIV alone did not consume complement and showed no opsonic activity by itself for these organisms. When these bacteria were preopsonized in IGIV, significant amounts of complement were consumed (44%-94%) and the uptake and killing of bacteria occurred. The in vitro opsonic activity of IGIV for these organisms was significantly correlated with the amount of complement consumed by the IGIV-opsonized bacteria (r = .85, P less than .05). The in vivo protective efficacy of IGIV also appeared to be directly associated with its ability to activate and consume complement (r = 1.0, P less than .001). Antibodies to FcRlo (Leu 11) markedly inhibited phagocytosis of bacteria opsonized in IGIV but not that of bacteria opsonized in specific IgM. Both CR1 and CR3 receptors on PMNLs were involved in uptake, but the contribution of each is different with different organisms.

Effects of fibronectin on the interaction of polymorphonuclear leukocytes with unopsonized and antibody-opsonized bacteria

Fibronectin (Fn) affects the interaction of polymorphonuclear leukocytes (PMNLs) with certain bacteria. Fn alone enhanced the response, in a chemiluminescence (CL) assay, of PMNLs to Staphylococcus aureus (P less than .05) and Staphylococcus epidermidis (P less than .01) but had no effect on type III, group B streptococci (GBS) or Escherichia coli. When GBS or E. coli were first preopsonized in antibody, Fn significantly enhanced the CL response of PMNLs (P less than .05). The intracellular metabolic inhibitor NaN3 but not the extracellular scavengers superoxide dismutase or human serum albumin inhibited Fn-enhanced CL; this fact suggests that enhancement of the respiratory burst by Fn is an intracellular event. We used an acridine orange-crystal violet monolayer assay to examine the effects of Fn on ingestion and intracellular killing of bacteria by PMNLs. Fn alone promoted uptake and killing of S. aureus (P less than .01) and S. epidermidis (P less than .05) by PMNLs but did not enhance monolayer phagocytosis of GBS or E. coli, unless these bacteria were preopsonized in antibody (P less than .01).