Measurement of phagocyte chemiluminescence in a microtitre plate format

Immunotoxicological and biochemical effects of aflatoxins in rats prevented by Tunisian montmorillonite with reference to HSCAS

BACKGROUND AND AIM

Previously we reported that hydrated sodium calcium aluminosilicate (HSCAS) and Tunisian Montmorillonite (TM) had an ability to sorb aflatoxins with a high affinity. Addition of these compounds to feedstuffs contaminated with aflatoxins has shown protective effects against the development of aflatoxicosis in farm and laboratory animals. The objective of the current study was to compare the efficiency of HSCAS and the TM in respect to the protection against immunotoxicological effects of aflatoxins in rats.

MATERIALS AND METHODS

Animals fed an aflatoxin-contaminated diet (2.5 mg/kg diet) showed a significant decrease in all hematological parameters, cholesterol, triglycerides, cholinesterase, total protein, albumin, zinc and copper concentrations.

RESULTS

Such feeding significantly increased createnine, bilirubin, urea nitrogen, alkaline phosphatase and transaminases concentrations. The immunological results showed a significant decrease in lymphocytes of the total white blood cells, immunoglobulin profile (Ig G and Ig A), T-cells sub-types (CD3(+), CD4(+) and CD8(+)), NK and pro-inflammatory cytokines (TNFalpha and IL-1beta) typical of aflatoxicosis. Both HSCAS and TM at the level of 5 g/kg contaminated diet resulted in a significant improvement in all immunological parameters-in lymphocyte, immunoglobulin profile, T-cells sub-types and pro-inflammatory cytokines as well as the mineral status and the biochemical parameters.

CONCLUSIONS

The deleterious effects of aflatoxin could be overcome or, at least, diminished by the addition of sorbents. Moreover, both tested sorbents by themselves had no toxic effects and bind aflatoxin with high affinity.

Measurement of whole blood phagocyte chemiluminescence in a microtitreplate format

Zymosan-induced luminol-enhanced chemiluminescence of phagocytes was measured in whole blood using a microtitreplate format. A consistent reaction response curve could be obtained using a normal blood sample, with low intra-assay variations in peak light index, cumulated response as well as time taken to reach the peak. Variations were common when tests were done on different days for the same individual, or when different persons were compared simultaneously. Reactions were hastened and enhanced if continuous shaking at 37 degrees C was applied. The interval between time zero and peak was the most consistent variable, with a coefficient of variation of 12% in inter-assay analysis. Because of its simplicity and ease of operation, the method is potentially useful in studying phagocyte functions in pathological states.

Fiber-optic biosensor to assess circulating phagocyte activity by chemiluminescence

We describe herein the construction of a novel computerized multi-sample temperature-controlled luminometer for a fiber array-based biosensor to monitor circulating phagocyte activity. It can perform simultaneously integral measurements of chemiluminescence emitted from up to six samples containing less than 0.5 microl whole blood while the samples and detector do not change their position during the measurement cycle. The optical fibers in this luminometer are used as both light guides and solid phase sample holders. The latter feature of the instrument design simplifies the assessment process of both the extra-cellular and the intra-cellular parts of the phagocyte-emitted chemiluminescence using the same system. We describe some examples or proof of principle for the use of the biosensor. This new technology may find use in a wide range of analytical luminescence applications in biology, biophysics, biochemistry, toxicology and clinical medicine.

Development of a respiratory burst assay using zebrafish kidneys and embryos

The innate immune response constitutes the first line of defense against invading pathogens and consists of a variety of immune defense mechanisms including the respiratory burst of phagocytes. Respiratory burst can be used as a reliable measure of the immune response of a host, and numerous assays have been developed to measure this response in a variety of mammal and fish species. Phagocytes, like granulocytes and macrophages, that are derived from different tissues, or grown in cell culture, have been employed in a range of assay formats employing a variety of detection methods. The small size of the zebrafish has prevented the large-scale extraction of these cells for respiratory burst assays in the zebrafish. In this work, we describe a respiratory burst assay developed for the zebrafish using intact kidneys and embryos as sources of phagocytes. Phorbol myristate acetate (PMA)-inducible reactive oxygen species (ROS) were detected following the oxidation of a non-fluorescent dye 2',7'-dihydrodichlorofluorescein diacetate (H2DCFDA) to dichlorofluorescein (DCF), a fluorescent product. Embryos from 1 day post-fertilization until 5 days post-fertilization (dpf) were employed in this assay. Abrogation of H2DCFDA oxidation by the protein kinase C (PKC) inhibitor bisindolylmaleimide I (BisI) indicated a reduction in the respiratory burst. Fluorescence from the PMA-induced respiratory burst in kidneys and embryos was significantly elevated above DMSO-treated controls, while preincubation with BisI inhibited the increase in fluorescence. Colocalization of cell-associated chloromethyl-dihydrodichlorofluorescein diacetate (CM-H2DCFDA) with the phagocyte-selective dye neutral red is consistent with the observation that macrophages and granulocytes are the ROS-producing cells in the zebrafish.

Effects of long-distance running on serum opsonic activity measured by chemiluminescence

Exhaustive exercise such as long-distance running has been shown to increase susceptibility to infection. In order to investigate whether serum opsonic activity plays a role in such conditions, we utilized luminol-dependent and lucigenin-dependent chemiluminescence (LmCL and LgCL). We took serum samples from 24 male marathon runners before and after running 30 km. Neutrophils were isolated from the peripheral blood of healthy volunteers. Serum opsonic activity was examined by measuring neutrophil ROS stimulated with zymosan particles opsonized by the serum samples. Immunoglobulin and complement levels in the serum were also measured. After a 30 km run, the maximum light emission was increased and the time to reach the maximum light emission was shortened significantly (p < 0.05) in LmCL. However, there were no significant changes in the immunoglobulin and complement levels. The increase of ROS production may suggest that serum opsonic activity is accelerated after running 30 km. Thus, serum opsonic activity might not play a significant role in the susceptibility to infection after long-distance running.

Effects of liposome-encapsulated ciprofloxacin on phagocytosis, nitric oxide and intracellular killing of Staphylcoccus aureus by murine macrophages

The effects of liposome-encapsulated ciprofloxacin on phagocytosis, nitric oxide production and intracellular killing of Staphylococcus aureus in murine macrophages were evaluated in this study. Mice were pretreated with three daily doses of liposome-encapsulated ciprofloxacin (45 mg/kg body weight/dose, intraperitoneal injection). At day 3 post drug administration, peritoneal macrophages were harvested by peritoneal lavage, and the phagocytic activity of the macrophages was determined by a chemiluminescence assay using opsonized zymosan particles. The phagocytic activity was found to be 7-fold higher in the liposome-encapsulated ciprofloxacin-treated group when compared to the untreated control group. For S. aureus-infected macrophages incubated with liposomes containing subinhibitory concentrations of ciprofloxacin (0.05 to 0.25 microg/mL), there were significant increases (up to 40 microM) in the levels of nitrite (NO2-, an end product of nitric oxide synthesis), and concommitant decreases (2-3 log) in the intracellular concentrations of S. aureus. Peak nitrite levels (20-40 microM) were produced when concentrations of liposome-encapsulated ciprofloxacin used were 0.1 to 0.25 microg/mL. These results suggest that liposome-encapsulated ciprofloxacin may have profound effects on the immunological functions of macrophages.

Optimization of phagocyte chemiluminescence measurements using microplates and vials

In order to cope with large amounts of samples for chemiluminescence (CL), vials were replaced with microplates. Although various types of plates have been commercially available for quite some time and the free-plate mode is advocated by the producer of the counter, little is known about their impact on the outcome of CL measurements. We tested two different 24-well microplates and six different 96-well microplates in two different luminometers, and results were compared with those achieved with vials. Before these comparative tests, we attempted to optimize measurement conditions. CL sensitivity was highest with luminol concentrations of 0.8-3.3 micromol/L, PMA concentrations of 0.06-80 micromol/L, a pH value of 10 and a temperature of 20 degrees C. An indirect correlation was found between fluid volume and yield in counts: the lower the volume, the higher the counts. With regard to sensitivity and cross-talk, the 96-well Isoplatetrade mark was superior to all other plates tested. While all white plates tested gave acceptable results, usage of the black 96-well plates resulted in an extremely low sensitivity. Plates designed for cell culturing gave even lower counts and a cross-talk of up to 31%. All attempts to reduce cross-talk and improve sensitivity, such as aluminium foil or grids, irrespective of the position of the photomultiplier, did not give results comparable to the original 96-well isoplate. Our results suggest that, with the exception of black 96-well microplates and cell culture plates, all other plates tested have a sufficient sensitivity when compared to vials and acceptable cross-talk, the 96-well Isoplatetrade mark being the best. Both types of luminometers used gave reproducible results, Wallac having a somewhat higher sensitivity, Canberra Packard somewhat less cross-talk.

Analysis and assessment of the capacity of neutrophils to produce reactive oxygen species in a 96-well microplate format using lucigenin- and luminol-dependent chemiluminescence

The chemiluminescence (CL) assay has been used to measure the reactive oxygen species (ROS)-generating capacity of phagocytes. To achieve more optimal measurement conditions for a multi-channel microplate photon-counting CL analyzer with the cooled charge-coupled device (CCD) camera which offers enhanced sensitivity, we investigated factors affecting the variability in lucigenin-dependent CL (LgCL) measurement of human neutrophils stimulated with either opsonized zymosan (OZ) or phorbol myristate acetate (PMA). We obtained sensitive LgCL responses with good reproducibility and rapid data-acquisition using 50 microl neutrophils (3 X 10(6) cells/ml) and 50 microl of 0.5 mM lucigenin per well, in addition to either 100 microl of OZ (5 mg/ml) when zymosan was opsonized with 10-20% serum or 100 microl of PMA solution (1 X 10(-6) M) with automatic regular intervals of mixing and detection during the continuous measurement at 37 degrees C. Furthermore, we studied the contribution of various ROS to LgCL and luminol-dependent CL (LmCL) using modulators of ROS metabolism including superoxide dismutase (SOD), catalase, deferoxamine and sodium azide (NaN3). LgCL was inhibited by SOD but not by the other agents, whereas LmCL was inhibited by NaN3 and deferoxamine. Thus, it was demonstrated that LgCL detects the superoxide anion with high selectivity whereas the LmCL assay measures myeloperoxidase (MPO)-mediated formation of hypochlorous acid. Such microplate-based multiple measurements facilitate the accurate assessment of phagocytic function.

Effect of in vitro maedi-visna virus infection on adherence and phagocytosis of staphylococci by ovine cells

This work was aimed at studying the effect of maedi-visna virus (MVV) infection in vitro on the ability of sheep cells to adhere to staphylococci (Staphylococcus aureus and Staphylococcus epidermidis), and phagocytose these bacteria. Adherence was studied in sheep choroid plexus cells (SCPC) using an ELISA test and phagocytosis was studied in pulmonary alveolar macrophages (PAM) by chemiluminescence. A 5- and 7-day of in vitro MVV infection resulted in syncytium formation and a significant increased adherence (P < 0.01) of SCPC to bacteria. SCPC endogenous fibronectin was significantly higher (P < 0.01) on days 5 and 7 than on day 0 of MVV infection. A significantly decreased phagocytosis (P < 0.05) was also observed on days 5 and 7 of MVV infection in PAM when compared to MVV-free controls. Comparatively, phagocytosis was highest for S. aureus non-slime producing strains, followed by S. epidermidis, and S. aureus slime producing strains, in that order. Finally, increased expression of both, class I and class II major histocompatibility antigens was also observed in MVV-infected PAM on days 5 and 7, whereas SCPC only demonstrated upregulation of MHC class I. These results, indicative of an alteration of some cell functions in MVV-infected cells, may help to understand interactions between MVV-infected cells and bacteria in simultaneous infections and may provide clues to the possible in vivo interactions of both pathogens.

Influence of age on the release of reactive oxygen species by phagocytes as measured by a whole blood chemiluminescence assay

Polymorphonuclear and mononuclear phagocytes play an important role in host defense, but may also cause tissue injury through excessive inflammation. Reactive oxygen species (ROS) are not only directly ore indirectly involved in a wide variety of clinical disorders, such as atherosclerosis, reperfusion injury, pulmonary toxicity and cancer, but they are also important in the aging process. This process is associated with increasing susceptibility to infection. In this study we investigated the influence of age and sex on phagocyte activation by means of a whole blood chemiluminescence (CL) assay. Circulating phagocyte activity was measured in 55 healthy volunteers (24 females, 31 males) aged from 6 to 92 years. Using an automated luminescence system, phagocytes were stimulated by polystyrene beads and Luminol-enhanced CL was determined in terms of peak height and peak time in freshly withdrawn, peripheral venous whole blood. An extremely significant positive correlation (p < 0.0001) between the maximum of light emission after stimulation and increasing age was found. This finding is true for the total population of blood phagocytes as well as for a single cell. In contrast the time of the appearance of the maximum of light emission showed an extremely significant inverse correlation (p < 0.0003) with increasing age. The influence of sex on the CL-parameters showed no significant difference between women and men. It is concluded that the increased susceptibility of circulating phagocytes to oxidative burst in elderly subjects may be the consequence of several biological events. Senescent cells express more and also have new antigens on their surfaces that trigger an autoimmune response. Cellular senescence appears earlier in old organisms. Therefore phagocytes in aging individuals may be increasingly involved in their scavenger tasks that grow with the catabolic bias in cell turnover. Moreover, atherosclerotic alterations in the intima and endothelial lesions are physiologic concomitants of age and may lead to a stimulation of circulating phagocytes.

The effect of cefodizime on phagocyte function in non-patient volunteers and patients with chronic renal failure. In vitro and ex vivo studies

Cefodizime has previously been shown to possess a number of immunomodulating properties in vivo and in vitro using several different test systems. Since most in vitro studies have been performed with cells from normal individuals, we first investigated whether cells from chronic renal failure patients would respond in vitro to cefodizime in the same way as healthy subjects. Subsequently, we investigated the effect of cefodizime (10 g over 10 days in 2-g doses) on phagocyte function ex vivo in an open study of 26 chronic renal failure patients and 16 healthy subjects. Polymorphonuclear leukocytes were tested for their ability to polarize in response to cefodizime and/or f-met-leu-phe peptide. Polymorphonuclear leukocytes and monocytes were tested for their ability to produce chemiluminescence on stimulation with either phagocytic (zymosan) or soluble phorbol myristate acetate stimuli. Phagocyte and lymphocyte membrane receptor expression was compared after exposure to cefodizime. Exposure to cefodizime in vitro causes a significant increase in polarization of polymorphonuclear leukocytes from both normal individuals and renal failure patients (both P < 0.001). It also caused increased chemotaxis and chemokinesis in a modified Boyden chamber assay. Cefodizime did not affect lucigenin-enhanced chemiluminescence and there were only minor effects on cell membrane antigen levels. In the ex vivo study there was a significant increase in polymorphonuclear leukocyte polarization (P < 0.001) attributable to cefodizime, but other investigations showed no significant differences. The results suggest that cefodizime may act as a mild priming agent for some functions, particularly chemotaxis.

Enhanced mitochondrial radical production in patients which rheumatoid arthritis correlates with elevated levels of tumor necrosis factor alpha in plasma

Mitochondrial dysfunction contributes to cell damage in a number of human diseases. One significant mechanism by which mitochondria damage cells is by producing reactive oxygen species from the respiratory chain. In this study we measured the production of reactive oxygen species by leukocyte mitochondria in blood from rheumatoid arthritis patients. To do this we used the chemiluminescence of lucigenin, which is accumulated by mitochondria within cells and reacts with superoxide to form a chemiluminescent product. By using specific inhibitors we could distinguish between the production of reactive oxygen species by mitochondria and by NADPH oxidase. There was a five-fold increase in mitochondrial reactive oxygen species production in whole blood and monocytes from patients with rheumatoid arthritis, when compared to healthy subjects or patients with non-rheumatic diseases. There was no increases in mitochondrial reactive oxygen species production by neutrophils from rheumatoid arthritis patients. The enhanced mitochondrial radical production in rheumatoid arthritis patients correlated significantly with increased levels of tumor necrosis factor alpha in plasma (p < 0.0001). As tumor necrosis factor alpha is known to increase mitochondrial reactive oxygen species production the elevated mitochondrial radical formation seen in rheumatoid arthritis patients may be due to activation of the mitochondrial radical production. These data suggest that elevated mitochondrial oxidative stress contributes to the pathology of rheumatoid arthritis.

Priming of NADPH oxidase by tumor necrosis factor alpha in patients with inflammatory and autoimmune rheumatic diseases

Oxidative damage caused by oxygen free radicals from activated phagocytes contributes to the pathology of arthritis. The present study evaluates the activity of NADPH oxidase of neutrophils and monocytes from patients suffering from various inflammatory and autoimmune rheumatic disease. Production rates of reactive oxygen species [ROS] of neutrophils and monocytes from rheumatic patients are compared to those of healthy controls and non rheumatic disease controls and correlated with the plasma levels of tumor necrosis factor alpha, C-reactive protein and the sedimentation rates of erythrocytes. There was a two- to eightfold increase in phagocytic superoxide production in rheumatic patients, when compared to healthy subjects or patients with non-rheumatic internal diseases [p < 0.005]. The enhanced NADPH oxidase-dependent superoxide generation correlated well with elevated levels of tumor necrosis factor alpha [TNF-alpha] in plasma [p = 0.005], suggesting a causal relation. There was no correlation with the plasma levels of C-reactive protein and a weak though significant correlation with the sedimentation rates of erythrocytes [p = 0.043]. Removal of circulating TNF-alpha by dialysis of patients blood and inhibition of NADPH oxidase by prednisolone treatment normalized elevated ROS production to the levels of healthy controls and correlated with the clinical improvements. Our data support the hypothesis of a central role for TNF-alpha during the development of arthritis. The chemiluminescence assay described here may be useful as a convenient screen and as a potential follow up procedure for individual patients with rheumatic diseases.

Phagocyte chemiluminescence in pre-term infants

Intact phagocyte function is a pre-requisite for successful defence against infection, but paradoxically, these cells may also play a major role in the pathogenesis of the infant respiratory distress syndrome. Phagocyte function is known to be deficient in pre-term infants, who are at risk of infection as a result, but these infants are also at risk of respiratory distress syndrome as a result of surfactant deficiency. Despite this, few longitudinal studies of phagocyte function have been performed in pre-term infants. We have used lucigenin-enhanced chemiluminescence to examine the respiratory burst of mixed samples containing polymorphonuclear leucocytes and monocytes of 100 pre-term infants at 48- to 72-h intervals during their admission to a neonatal care unit. Increased polymorphonuclear leucocyte chemiluminescence was associated with respiratory distress syndrome and the use of intermittent positive pressure ventilation. Multiple linear regression analysis revealed a slight, but significant depression of chemiluminescence in association with the use of gentamicin and penicillin when stronger influencing factors such as the presence of respiratory distress syndrome were taken into consideration. Measurement of phagocyte function by sensitive luminescence assays requires very little blood and may be useful in pre-term infants to follow the severity of respiratory distress syndrome. However, it is probable that other factors such as antioxidant capacity also have an important influence on the degree of tissue damage.

Antibiotic effects on phagocyte chemiluminescence in vitro

Phagocytes are an essential defence against infection. Since drugs which affect their function may alter the outcome of infections, we have studied the effect of nine antibiotics on phagocyte function in vitro. The effects of antibiotics on the respiratory burst function of phagocytes from healthy adult donors were investigated using lucigenin-enhanced chemiluminescence in response to serum-opsonised zymosan. Aminoglycosides showed dose-dependent suppression of polymorphonuclear leucocyte chemiluminescence, except streptomycin which caused enhancement. Erythromycin caused profound suppression of chemiluminescence from both polymorphonuclear leucocytes and monocytes. Benzylpenicillin and the cephalosporins caused variable suppression of phagocyte chemiluminescence: cefotaxime increased monocyte chemiluminescence in some experiments. None of the drugs produced suppression at clinically relevant plasma concentrations, but erythromycin and some other drugs are preferentially concentrated in phagocytes to levels which suppress their oxidative metabolism in vitro. It is therefore possible that some antibiotics alter phagocyte function: ex vivo studies of phagocyte function in patients taking antibiotics would be valuable.

Optimization of a phagocyte microplate chemiluminescent assay

Chemiluminescent assays have been used to quantify phagocytic activity since 1972. In recent years these assays have been adapted to the 96-well microplate format as new luminometers have been developed. In this report we describe the optimization of a lucigenin enhanced phagocyte chemiluminescent assay using a Titertek Luminoskan. Factors such as cell concentration, serum concentration in the opsonization of the zymosan used and lucigenin concentration were all optimized in our assay. In addition we have found that some of the unique features of the Luminoskan, continuous microplate agitation during the assay and microplate temperature control up to 43 degrees C, also significantly enhanced the chemiluminescent response.

The influence of age and sex on phagocyte chemiluminescence

The process of ageing is associated with increased susceptibility to infection. Phagocytes form the primary defence mechanism against infecting microorganisms, but the influence of ageing on phagocyte function remains controversial. In this study we have applied a microtitre plate phagocyte chemiluminescence (CL) assay suitable for clinical use to compare phagocyte oxidative metabolism in younger healthy subjects (age 20-60 years) and healthy older (60-70 years) subjects. Polymorphonuclear leukocytes (PMNL) and monocytes were stimulated using phorbol myristate acetate (PMA), serum opsonized zymosan (SOZ), and non-opsonized zymosan (ZYM) in the presence of both lucigenin and luminol. Monocytes showed a higher luminol-enhanced CL response to PMA in males compared with females in the younger age group. No PMNL differences were observed between the sexes. Although no differences were found in relation to age when cells were stimulated with PMA and SOZ, significantly lower background (unstimulated) CL was obtained from PMNL with luminol. PMNL luminol-enhanced CL responses were also lower in response to ZYM. The findings suggest a reduced response of PMNL from older subjects to minimal stimulation. This could be related to abnormalities in the triggering of the respiratory burst or myeloperoxidase release due to ageing. The influence of age and sex should be taken into account in clinical studies of phagocyte CL.

Phagocyte function and cytokine production in community acquired pneumonia

BACKGROUND

It is possible that many deaths from pneumonia may involve the generation of inflammatory mediators and tissue damage by activated phagocytes. To test this hypothesis phagocyte function, plasma levels of interleukin 6 (IL-6), tumour necrosis factor alpha (TNF alpha), and soluble interleukin 2 receptor (IL-2R), disease severity, and outcome have been examined in 46 patients with community acquired pneumonia.

METHODS

Polymorphonuclear leucocyte (PMNL) and monocyte function were measured daily by chemiluminescence in these patients during the first week of admission, and cytokine levels were subsequently determined by ELISA. A series of 61 healthy individuals were used as a control group for the chemiluminescence results.

RESULTS

There was evidence of phagocyte, particularly PMNL, activation on admission in 76% of the patients. Most patients (86%) also had raised IL-2R levels on admission. IL-6 and unbound TNF alpha were present in 23% and 41% of patients at varying times during the course of the disease. There was little correlation between measurements of cytokine or phagocyte levels and outcome or indicators of disease severity, although this may be because of the small number of patients included in this preliminary study.

CONCLUSIONS

These results are consistent with the hypothesis that activated phagocyte function and raised levels of circulating cytokines may contribute to the pathogenesis of community acquired pneumonia. There are striking similarities in this respect between pneumonia, adult respiratory distress syndrome, and sepsis.

Effect of salmeterol on polymorphonuclear leukocyte (PMNL) chemiluminescence in vitro

Although beta-agonists remain an important aspect of the treatment of asthma, their role has recently been questioned. Salmeterol has recently been developed as a beta-agonist with prolonged bronchodilator action. Using lucigenin-enhanced chemiluminescence, we have shown that salmeterol inhibits this aspect of phagocyte function in vitro in a concentration-dependent manner. However, salmeterol differs from classical beta 2-agonists in that at concentrations between 10(-5) and 10(-3) mol/L, its effects on phagocytes cannot be completely reversed by washing the cells or by propranolol. The effects on phagocytes may not therefore be explicable on the basis of beta-adrenergic mechanisms alone.

Heat-stable opsonins in tuberculosis and leprosy

We have examined heat-stable opsonins to 4 species of gamma-irradiated mycobacteria (M. tuberculosis (H37Rv), M. avium (28A), M. scrofulaceum and M. leprae (cd 103)) in complement-depleted sera collected from Indonesian subjects with tuberculosis (106 patients),-leprosy (24 patients) and controls (40 hospital workers and 41 factory workers) indirectly by microtitre plate chemiluminescence (CL) assay and compared the results with antibody levels. The results indicate that there is a wide range of opsonic capacity for mycobacteria in complement-depleted sera. There was a poor correlation between the opsonic capacity as measured by CL and the anti-mycobacterial antibody content of sera measured by ELISA, suggesting that anti-mycobacterial antibody has little influence on the uptake of mycobacteria. However, a non-specific heat-stable opsonin appears to be present in some sera. Conversely, some sera from tuberculosis or leprosy patients suppress the production of reactive oxygen species from normal phagocytes in vitro when stimulated with M. tuberculosis. The relevance of this inhibition and the presence of heat-stable opsonins to the pathogenesis of tuberculosis have yet to be determined, but it is possible that the presence of opsonins may inhibit dissemination of tubercle bacilli to other organs.

Impaired functions of normal peripheral polymorphonuclear leukocytes in cirrhotic ascitic fluid

The function of normal polymorphonuclear cells in the ascitic fluid of 32 patients with cirrhotic ascites and 17 patients with malignant ascites was studied independently of ascitic fluid heat-labile factors. Polymorphonuclear (PMN) function was assessed by a chemiluminescence method using preopsonized zymosan as stimuli. The chemiluminescence response was higher in malignant ascitic fluid than in cirrhotic ascitic fluid (0.84 and 0.15, respectively, p < 0.001). These results were confirmed by a microbiological assessment of phagocytosis. Suppressive factors were evidenced by making ascitic fluid dilutions and using cell-free chemiluminescence measurements. Addition of malignant ascitic fluid to cirrhotic ascitic fluid showed that there is also a deficiency in supportive factors other than C3. The impaired PMN production of oxidative metabolites we observed in cirrhotic ascitic fluid can partly explain the high susceptibility of cirrhotic patients to spontaneous bacterial peritonitis independently of C3 levels.

Enhancement of normal polymorphonuclear cells respiratory burst in ascitic fluid by fibronectin. Comparison between cirrhotic and malignant ascitic fluids

The chemiluminescence (CL) response of normal peripheral blood polymorphonuclear cells (PMN) in ascitic fluids (cirrhotic = 32; malignant = 17) was studied independently of the ascitic fluid complement activity. CL response and fibronectin levels were higher in malignant ascitic fluid than in cirrhotic ascitic fluid (p less than 0.001). Addition of pure fibronectin or malignant ascitic fluids to cirrhotic ascitic fluids increased the CL response of normal PMN. These findings suggest that the susceptibility of cirrhotic patients to spontaneous bacterial peritonitis (SBP) is a multifactorial defect involving factors distinct from low C3 levels. Fibronectin is an important factor in the promotion of the respiratory burst of normal PMN stimulated by opsonized zymosan or PMA in ascitic fluid. Our results suggest that low levels of ascitic fluid fibronectin could partly explain the high susceptibility of cirrhotic patients to spontaneous bacterial peritonitis.

Simultaneous detection of whole blood chemiluminescence in microtitre plates

The measurement of reactive oxygen species provides a simple method for monitoring the degree of activation of leukocytes in various disorders, and for determining the effects of drugs on this activation. The present report describes the determination of luminol- or lucigenin-amplified chemiluminescence of whole blood in a microtitre plate assay with a 96-well luminometer (HAMAMATSU MTP reader). Using heparinized venous human blood from healthy donors, optimal chemiluminescence intensities were determined at a blood dilution of 1/100 in a total volume of 0.25 ml of Hank's balanced salt solution, containing 0.4 mmol/l luminol as enhancer and either opsonized zymosan (1 milligram) or the phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (10(-6) mol/l), as stimuli. The in vitro effects of nordihydroguaiaretic acid, diphenylene iodonium, and diclofenac were tested. After preincubation of the diluted whole blood with these drugs for 15 min, the zymosan-stimulated chemiluminescence was diminished in all cases. The specific NADPH oxidase inhibitor, diphenylene iodonium, was most effective (half maximal inhibition at 1.5 x 10(-8) mol/l), whereas higher concentrations of the antioxidant, nordihydroguaiaretic acid (1.6 x 10(-6) mol/l), or the nonsteroidal antiinflammatory drug, diclofenac (about 10(-5) mol/l), were needed to achieve half maximal inhibition. In addition to its usefulness in the rapid screening of drug effects this assay system seems to be very beneficial for the clinical diagnosis of congenital disorders. Furthermore, it is suited as an effective and simple method for the continuous determination of the phagocyte functional state in patients in pathophysiological situations and during therapy.

Studies on chemiluminescence and protein kinase-C activity of cisplatin treated mouse peritoneal exudate cells

A single i.p. injection of cisplatin (10 mg/kg body weight) into mice results in a significant increase in chemiluminescence and ATP contents of the peritoneal exudate cells (PEC) than that of PEC from untreated mice. It is also observed that in vitro treatment of macrophages with cisplatin, rIFN-gamma and LPS show increased activity of the protein kinase-C (PK-C). The activation of PK-C could result in stimulation of NADPH-oxidase resulting in increased levels of chemiluminescence. Increased contents of ATP in PEC after cisplatin treatment also suggests that this activation is energy dependent.

Measurement of phagocyte chemiluminescence using a microtitre plate luminometer

The use of chemiluminescence techniques to study the interaction between bacteria and phagocytes has been useful for examining the extent to which serum factors, such as opsonins, are important in internalization of the organisms and the response of the cell to phagocytosed bacteria. However, such methods have been limited by the number of experiments which can be performed at one time using most commercial luminometers. However, the recent introduction of the Amerlite microtitre plate luminometer allows the measurement of chemiluminescence responses in 96-well microtitre plates. Using this instrument, lucigenin-enhanced chemiluminescence can be detected from as few as 5000 cells (polymorphonuclear leukocytes or monocytes) per well with a 1:10 ratio of cells to zymosan particles opsonized with 10% serum. The opsonic capacity of up to 100 sera can be measured in triplicate wells in a single experiment using four microtitre plates and polymorphonuclear leukocytes prepared from less than 40 ml freshly obtained venous blood. We are currently using this technique to investigate the effect of serum opsonins on the interaction between normal human polymorphonuclear leukocytes and monocytes with mycobacteria of three species (Mycobacterium leprae, M. tuberculosis, and M. avium-intracellulare). Other possible applications of this method are discussed.

Use of a microtitre plate chemiluminescence reader to study surface phagocytosis by human monocytes

Human mononuclear cells were separated from freshly obtained peripheral venous blood by density centrifugation and the number of monocytes present estimated by volume spectroscopy. The mononuclear cells were then placed directly into the wells of a microtitre plate and incubated for one hour at 37 degrees C to promote adherence of the monocytes to the plastic wells. Non-adherent cells were then removed by washing, thus avoiding the need to treat the monocytes with EDTA or other reagents during cell preparation. The time course and dynamics of the chemiluminescence response of adherent monocytes towards opsonized zymosan was similar to those seen using non-adherent cells. The ability of adherent monocyte preparations to produce chemiluminescence following incubation for varying periods with T-lymphocyte conditioned medium was investigated. The use of a microtitre plate chemiluminescence reader allows several plates to be assayed over the 24-hour period and since small numbers of cells are required, many cultures can be analysed in one experiment. This technique (Patent applied for) promises to be a powerful tool for dissecting the cellular events which occur during macrophage activation and examining the effect of various lymphokines on the ability of monocytes to produce a chemiluminescence response.