Macrophage oxygen-dependent antimicrobial activity. III. Enhanced oxidative metabolism as an expression of macrophage activation

A cytochemical study of the interaction between Tritrichomonas foetus and mouse macrophages

Light and electron microscopy were used to analyse the process of interaction of normal and antibody-coated Tritrichomonas foetus with resident and activated mouse peritoneal macrophages. Activated macrophages ingest more parasites than do resident macrophages. Previous incubation of the parasites in the presence of sub-agglutinating concentrations of a polyclonal anti-T. foetus antibody significantly increased their ingestion by the macrophages. Adherence of the parasites to the surface of activated macrophages triggers the respiratory oxidative burst as revealed by reduction of nitroblue tetrazolium. This process was more evident in antibody-coated parasites. Transmission electron microscopy showed the presence of reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H]-oxidase in the portions of the macrophage plasma membrane that were in contact with the parasites as well as in the phagocytic vacuoles. Fusion of macrophage lysosomes with parasite-containing phagocytic vacuoles was observed in macrophages labeled with Lucifer yellow and gold-labeled peroxidase as well as by localisation of acid phosphatase.

In vivo administration of recombinant growth hormone or gamma interferon activities macrophages: enhanced resistance to experimental Salmonella typhimurium infection is correlated with generation of reactive oxygen intermediates

Purified and recombinant forms of growth hormone (GH) as well as of recombinant rat gamma interferon (IFN-gamma) enhance the survival of rats deprived of endogenous pituitary GH secretion by hypophysectomy (HX rats) and infected with virulent Salmonella typhimurium. Macrophages obtained from rats with intact pituitaries (pituitary-intact rats) or HX rats that were treated in vivo with either GH or the closely related hormone prolactin released elevated (P less than 0.05) levels of superoxide anion (O2-) after in vitro opsonized-zymosan stimulation compared with those from placebo-treated animals. These levels of O2- release were similar in magnitude to those of macrophages from rats treated in vivo with IFN-gamma. In time course in vivo macrophage activation studies, both IFN-gamma and GH significantly increased O2- secretion within 24 h, with maximal secretion occurring at day 3. Macrophages obtained from pituitary-intact and HX rats injected in vivo with GH also released elevated (P less than 0.05) levels of hydrogen peroxide (H2O2) and displayed enhanced (P less than 0.01) phagocytic activity toward opsonized Listeria monocytogenes in vitro. The mechanism of action of GH in vivo is likely to be a direct one because resident peritoneal macrophages from rats could be primed in vitro for enhanced secretion of O2- following triggering of these cells with opsonized zymosan. These data show that in vivo administration of two closely related pituitary hormones, GH and prolactin, can effectively prime macrophages, which is consistent with the hypothesis that GH mediates resistance to S. typhimurium by a direct stimulatory action on macrophages.

Effects of swimming exercise on the pathogenesis of acute murine Toxoplasma gondii Me49 infection

The effects of swimming exercise on the pathogenesis of acute murine toxoplasma infection were studied. Swimming (45 min/day) initiated on the day of inoculation with the avirulent Me49 strain of Toxoplasma gondii did not alter survival of infected mice. At a later stage of infection, daily swimming appeared to promote the recovery of appetite and weight gain. Immune activation was apparent in toxoplasma-infected mice, and swimming blunted splenic enlargement but not the respiratory burst activity of peritoneal exudate cells. Infection caused a significant elevation of serum tumor necrosis factor (TNF) levels which was attenuated by a daily swimming program. These data show that swimming exercise is not deleterious to mice acutely infected with T. gondii Me49 and that the more rapid recovery in exercised mice is associated with reduced serum TNF levels.

Effects of reactive oxygen intermediate scavengers on the antitoxoplasmic activity of activated macrophages

Obioactin, Lonomycin A, muramyl dipeptide, and scavengers of hydrogen radicals and of singlet oxygen were used to study the participation of.OH and 1O2 in the killing of Toxoplasma in cultures of glycogen-induced peritoneal macrophages. Both the scavengers of OH (diazabicyclooctane and histidine) and those of 1O2 (mannitol and sodium benzoate) failed to inhibit the multiplication of Toxoplasma in macrophages that were incubated with either Obioactin, Lonomycin A, or MDP. The results of these experiments demonstrate the apparent lack of an inhibitory effect of.OH and 1O2 on the multiplication of Toxoplasma, whereas the scavengers alone inhibited the growth of the parasites.

Suspended mouse peritoneal macrophages. Preparation and properties

Since macrophages (MPH) are able to adhere firmly to solid surfaces, the recovery of viable and functional MPH has proven to be extremely difficult. We have developed a simple method using agarose coating for preparing MPH and culturing the cells in suspension. Their properties were tested over 72 h. The oxidative burst declined with time, but could be restored using the lymphokine rich supernatant of pokeweed-stimulated mouse spleen cells. In contrast, phagocytosis and Candida intra-cellular killing remained unchanged.

Increased monocyte oxidase activity in cystic fibrosis heterozygotes and homozygotes

Freshly isolated monocytes from cystic fibrosis (CF) heterozygotes and homozygotes had significantly increased oxygen uptake and superoxide formation after surface glycoprotein stimulation than did monocytes from age- and sex-matched controls. Lack of differences among the genotypes in inhibition by simple sugars of the concanavalin A-stimulated superoxide production and lack of differences in concanavalin A-binding surface proteins suggested that different regulation of the oxidase pathway produced the increased oxygen uptake and superoxide formation in CF patients and carriers. This regulatory role is consistent with the predicted structure of the CF gene product. The results support the hypothesis that the mononuclear phagocytes of CF heterozygotes have a significantly increased ability to kill intracellular microbes and may confer a selective advantage to the host.

Increased intracellular killing of bacteria in vitro by monocytes of patients with metastatic melanoma before and during treatment with interferon-gamma and interferon-alpha

The effect of recombinant human interferon-gamma (rHuIFN-gamma) and interferon-alpha (rHuIFN-alpha) as in vivo stimuli for the activation of human monocytes was investigated on the basis of the bactericidal activity of peripheral blood monocytes in 11 patients with metastatic melanoma before and during treatment with interferons. Patients received increasing doses of rHuIFN-gamma and a fixed dose of rHuIFN-alpha, both administered subcutaneously three times a week. The rates of intracellular killing of Listeria monocytogenes and Salmonella typhimurium after in vitro phagocytosis by monocytes collected from melanoma patients before interferon treatment were increased (P less than 0.01) by a factor of 1.7 and 1.4, respectively, relative to the rate constants in blood monocytes of healthy donors. During treatment with the interferons, the rates of intracellular killing of the bacteria by patients' monocytes did not further increase. The findings underscore the immunogenicity of malignant melanoma and put into question the macrophage activating activity of IFN-gamma with respect to the bactericidal activity of monocytes.

Enhanced macrophage anti-microbial activity following dimethylnitrosamine exposure in vivo is related to augmented production of reactive oxygen metabolites

Previous results demonstrated that mice exposed in vivo to DMN were more resistant to both bacterial and tumor challenges. Furthermore, macrophages (M phi) isolated from these animals demonstrated increased functional properties. As reactive oxygen intermediates (ROI) represent a key mechanism of anti-microbial action, it was important to determine whether ROI levels in M phi were related to augmented anti-microbial action in animals exposed to DMN in vivo. Peritoneal exudate M phi elicited with either thioglycollate (TG), Con A or C. parvum (CP) were examined for the production of ROIs. TG-M phi, Con A-M phi and CP-M phi obtained from animals exposed to DMN showed increased superoxide anion (O2-) production in vitro following stimulation with either phorbol myristate acetate (PMA) or opsonized zymosan (Op-zym) when compared to vehicle M phi. ROI production by bone marrow-derived macrophages (BMDM) produced by either GM-CSF or CSF-1 was also determined. BMDM from DMN-exposed animals obtained using either growth factor, had increased ROI production at 3, 5, 7 and 9 d of culture compared to vehicle BMDM. There was no shift in the kinetics of ROI production during differentiation of these BMDM. Analysis of extracellular anti-listericidal activity of TG- and CA-elicited M phi demonstrated that only TG-M phi obtained from DMN-exposed animals had enhanced killing capacity. There were no differences in intracellular anti-microbial activity in TG- and CA-elicited M phi obtained from either vehicle or DMN-exposed animals. TG-elicited M phi from either vehicle or DMN-exposed animals were examined for anti-microbial activity and H2O2 production following in vitro exposure to PMA. M phi from both vehicle and DMN treatment groups had enhanced killing and H2O2 production following PMA treatment, while PMA-stimulated TG-M phi from DMN-exposed animals demonstrated significantly higher levels of H2O2 production and cell killing as compared to all other treatment groups. These results suggest that previously observed increases in anti-microbial action by M phi from DMN-exposed animals are due in-part to enhanced ROI production.

The use of diphenylene iodonium, an inhibitor of NADPH oxidase, to investigate the antimicrobial action of human monocyte derived macrophages

Diphenylene iodonium is an inhibitor of the respiratory burst-generating NADPH oxidase of phagocytes. The effect of this compound on human monocyte-derived macrophages and its usefulness in exploring the antimicrobial mechanisms of phagocytes was examined. 1 microM diphenylene iodonium inhibited hydrogen peroxide production by human macrophages and the activity of these cells against Toxoplasma gondii. At this concentration macrophage degranulation was unaffected.

Bb fragment of bovine complement factor B: stimulation of the oxidative burst in bovine monocytes

In a previous study, we reported that fragment Bb of bovine complement factor B activated bovine monocytes, as demonstrated by the uptake of 3H-deoxyglucose. In the present study, the effects of Bb on the production of superoxide anion and hydrogen peroxide by bovine monocytes was investigated. The production of superoxide was measured by the superoxide dismutase inhibitable reduction of cytochrome c. The change in absorbance was determined by a spectrophotometer at a wavelength of 550 nm. Hydrogen peroxide production was measured by the horse-radish peroxidase-dependent oxidation of phenol red. The resulting color change was measured by a spectrophotometer at a wavelength of 620 nm. Fragment Bb (20 micrograms/mL) induced the generation of 0.96 +/- 0.2 (mean +/- SEM) nanomoles of superoxide/2.5 x 10(5) monocytes at 5 min. The production of superoxide peaked at 15 min (1.24 +/- 0.3 nanomoles). The production of hydrogen peroxide was also rapid: 0.195 +/- 0.05 nanomoles/2.5 x 10(5) monocytes at 5 min with a peak at 15 min (0.250 +/- 0.04 nanomoles). These observations show that fragment Bb, which has serine protease activity, induces bovine monocytes to generate reactive oxygen intermediates such as superoxide and hydrogen peroxide.

B-congenic chickens differ in macrophage inflammatory responses

The influence of the chicken major histocompatibility (B) complex (MHC) on monocyte and macrophage recruitment and activation was examined using fully developed 15I5-B congenic White Leghorn lines (ten backcross generations). The phagocytic activity of Sephadex-elicited peritoneal macrophages for sheep red blood cells (SRBCs) was highest in lines 15.7-B2 and 15.P-B13 and lowest in 15.15I-B5 and 15.N-B21. The same pattern of phagocytic activity was obtained when LPS (E. coli) was used as the in vivo elicitor-activator of peritoneal macrophages. Lines with B2 and B13 haplotypes had elevated percentages of phagocytic macrophages and a higher internalization activity per cell than did B5 and B21 congenic chickens. Differential peritoneal macrophage function between congenic lines was further supported by quantitation of superoxide anion release. B2 and B13 haplotypes were associated with high activity in contrast with B5, which was low, and 15I5 (B15) and B21 which were intermediate for superoxide anion release by macrophages. In vitro activation of blood monocytes with LPS resulted in similar line differences for SRBC phagocytic activity as were observed with in vivo Sephadex and LPS activation. In contrast, chemotaxis of blood mononuclear leukocytes to f-met-leu-phe produced a reciprocal response pattern among the haplotypes. Cells from lines with haplotypes B5 and B21 were superior to those of B2, B13, and B15 congenic lines in their directed migration towards this chemoattractant. All functional differences occurred despite similarities among lines in the cellular profiles of both elicited peritoneal exudate cells and isolated blood mononuclear cells.

Effects of immobilization stress on the pathogenesis of acute murine toxoplasmosis

Stress modulates a variety of immune responses. We investigated the effects of immobilization stress on the pathogenesis of acute murine toxoplasmosis, an infection in which cell-mediated immunity is of major importance in host defense. Repetitive overnight immobilization beginning 3 days prior to infection enhanced (p less than 0.05) the mortality of mice infected with a virulent strain (C56) of Toxoplasma gondii (77% vs 15% mortality in restrained and control mice, respectively). Daily immobilization for 14 days prior to infection abrogated (p less than 0.05) the lethal effect of immobilization, suggesting an adaptive mechanism. To explore the effect of immobilization with a less virulent strain, the Me49 strain of T. gondii was studied. Acute infection with T. gondii Me49 resulted in anorexia and weight loss, while spleen size and respiratory burst activity of peritoneal exudate cells were enhanced (p less than 0.01). Immobilization (twice daily for 2 h) did not significantly alter survival or other clinical features of acute T. gondii infection. In addition, immobilization suppressed (p less than 0.05) phorbol myristate acetate-stimulated release of superoxide anion by peritoneal exudate cells in healthy naive mice, but not in infected mice. These findings indicate that immobilization stress can alter the pathogenesis of acute T. gondii infection in healthy mice, but the effect of this stress paradigm will be influenced, in part, by the timing of the immobilization and the virulence of the strain of T. gondii.

In vivo activation of macrophage oxidative burst activity by cytokines and amphotericin B

Alterations in macrophage oxidative burst activity following in vivo administration of recombinant murine gamma interferon (IFN-gamma), recombinant murine tumor necrosis factor alpha, and the antifungal antibiotic amphotericin B were investigated. Mice were given intraperitoneal injections of these agents alone and in combination, and the oxidative responses of their resident peritoneal macrophages to challenge with Histoplasma capsulatum or zymosan particles were measured 1 to 5 days later. Various degrees of enhanced oxidative burst activity were achieved following treatment with each agent. However, a synergistic response was observed only when mice were treated with the combination of recombinant murine IFN-gamma and amphotericin B. These results not only confirm the dual role of amphotericin as an antifungal agent and as an immunomodulator but also suggest that IFN-gamma may serve as a useful adjunct in the treatment of intracellular fungal infections.

Interferon-gamma-activated human granulocytes kill ingested Mycobacterium fortuitum more efficiently than normal granulocytes

Although shortly after the onset of a mycobacterial infection granulocytes are present at the site of inflammation, the role of granulocytes in the elimination of mycobacteria is not well understood. In vitro studies with, for example Mycobacterium tuberculosis or M. bovis, are hampered by the slow proliferation and clumping of the bacteria. To avoid these disadvantages, we developed a model using the atypical mycobacterium M. fortuitum. The present study concerned two questions: whether human granulocytes are able to phagocytose and intracellularly kill opsonized M. fortuitum and whether intracellular killing of these bacteria can be enhanced by treatment of the granulocytes with recombinant human interferon-gamma (rIFN-gamma). The results showed that normal granulocytes phagocytosed opsonized M. fortuitum rapidly, but did not kill these bacteria effectively. The intracellular killing of M. fortuitum was significantly enhanced by incubation of the granulocytes with rIFN-gamma for 18 h before the start of the killing assay. Since these rIFN-gamma-pretreated granulocytes did not release more O2- and H2O2 upon stimulation with phorbol 12-myristate 13-acetate or opsonized M. fortuitum than control granulocytes, non-oxidative killing mechanisms are probably involved in the enhanced killing of M. fortuitum.

Oxygen-derived free radicals stimulate osteoclastic bone resorption in rodent bone in vitro and in vivo

The mechanisms by which bone resorbing osteoclasts form and are activated by hormones are poorly understood. We show here that the generation of oxygen-derived free radicals in cultured bone is associated with the formation of new osteoclasts and enhanced bone resorption, identical to the effects seen when bones are treated with hormones such as parathyroid hormone (PTH) and interleukin 1 (IL-1). When free oxygen radicals were generated adjacent to bone surfaces in vivo, osteoclasts were also formed. PTH and IL-1-stimulated bone resorption was inhibited by both natural and recombinant superoxide dismutase, an enzyme that depletes tissues of superoxide anions. We used the marker nitroblue tetrazolium (NBT) to identify the cells that were responsible for free radical production in resorbing bones. NBT staining was detected only in osteoclasts in cultures of resorbing bones. NBT staining in osteoclasts was decreased in bones coincubated with calcitonin, an inhibitor of bone resorption. We also found that isolated avian osteoclasts stained positively for NBT. NBT staining in isolated osteoclasts was increased when the cells were incubated with bone particles, to which they attach. We confirmed the formation of superoxide anion in isolated avian osteoclasts using ferricytochrome c reduction as a method of detection. The reduction of ferricytochrome c in isolated osteoclasts was inhibited by superoxide dismutase. Our results suggest that oxygen-derived free radicals, and particularly the superoxide anion, are intermediaries in the formation and activation of osteoclasts.

Regulation of cytoplasmic pH in resident and activated peritoneal macrophages

Cytoplasmic pH (pHi) has been shown to be an important determinant of the activity of the NADPH oxidase in phagocytic cells. We hypothesized that a difference in pHi and/or its regulation existed between activated and resident macrophages (RES MOs) which might explain the increased NADPH oxidase activity observed in the former. The pHi of RES and lipopolysaccharide (LPS)-elicited MOs was examined using the fluorescent dye BCECF. Resting pHi did not differ between resident (RES) and elicited (ELI) MOs (7.16 +/- 0.05 and 7.20 +/- 0.05, respectively). pHi recovery after intracellular acid loading was partially dependent on the presence of Na+ in the extracellular medium, and was partially inhibited by the Na+/H+ antiport inhibitor, amiloride. At comparable pHi, the rate of acid extrusion during recovery was not different in RES and ELI MOs (1.48 +/- 0.12 and 1.53 +/- 0.06 mM/min, respectively). In both RES and ELI MOs, approx. 40% of total pHi recovery was insensitive to amiloride and independent of extracellular Na+. In both RES and ELI MOs, stimulation with TPA resulted in a biphasic pHi response: an initial acidification followed by a sustained alkalinization to a new steady-state pHi. This alkalinization was Na(+)-dependent and amiloride-sensitive, consistent with a TPA-induced increase in Na+/H+ antiport activity. The new steady-state pHi attained after TPA stimulation was equivalent in RES and ELI MOs (7.28 +/- 0.04 and 7.31 +/- 0.06, respectively), indicating comparable stimulated Na+/H+ antiport activity. However, the initial acidification induced by TPA was greater in ELI than in RES MOs (0.18 +/- 0.02 vs. 0.06 +/- 0.02 pH unit, respectively, P less than 0.05). The specific NADPH oxidase inhibitor diphenylene iodonium (DPI) completely inhibited the respiratory burst but reduced the magnitude of this pHi reduction by only about 50%. This suggested that the TPA-induced pHi reduction was due in part to acid produced via the respiratory burst, and in part to other acid-generating pathways stimulated by TPA.

Toxic oxygen metabolite production by circulating phagocytic cells in inflammatory bowel disease

To investigate the possibility that the oxidative capacity of phagocytic cells may be defective in inflammatory bowel disease, toxic oxygen metabolite production by circulating neutrophils and monocytes has been measured by luminol dependent chemiluminescence. Neutrophils from patients with Crohn's disease and ulcerative colitis produced significantly lower chemiluminescent responses after chemotactic stimulation with formylmethionylleucylphenylalanine (fMLP) than neutrophils from control patients, p = 0.018 and 0.043 respectively. Chemiluminescent responses of neutrophils from patients with inflammatory bowel disease, however, were similar to control responses when cells were stimulated with latex beads or phorbol myristate acetate. Monocytes from patients with Crohn's disease produced significantly greater levels of chemiluminescence than control monocytes when stimulated with either fMLP (p less than 0.002), phorbol myristate acetate (p less than 0.0005) or latex beads (p less than 0.002). Monocytes from patients with ulcerative colitis also produced significantly greater levels of chemiluminescence than controls when stimulated with latex beads (p less than 0.5) or phorbol myristate acetate (p less than 0.0005), although there was no difference in the level of chemiluminescence in response to fMLP. These results exclude a generalised defect in phagocytic cell oxidase activity in inflammatory bowel disease and suggest that circulating monocytes are 'activated'.

Effect of tuftsin stimulation on the microbicidal activity exerted by blood monocyte-macrophages of leprosy patients

The ability of blood monocyte/macrophages from normal donors, tuberculoid leprosy (BT/TT) and lepromatous leprosy (BL/LL) patients to exert enhanced microbicidal activity was assayed after stimulating with 0.8 microM tuftsin, as a function of the duration of cultures in vitro. Normal and BT/TT macrophage cultures showed a statistically significant increase in microbicidal activity against Staphylococcus aureus at all ages of culture (6 h to 14 days), though the overall magnitude of the enhancement shows a decrease with increasing culture age in the same populations. However, 14-day old BL/LL macrophage cultures were unable to undergo tuftsin-mediated stimulation of microbicidal activity against S. aureus and even, fresh 6 h-old cultures exhibited a tuftsin-stimulated response profile similar to 14-day old normal and BT/TT cultures. Also, 7 and 14-day cultures of normal, BT/TT and BL/LL macrophages were unable to inhibit/kill intracellular Mycobacterium leprae after a single stimulation with 0.8 microM tuftsin. However, serial, daily stimulation with 0.8 microM tuftsin resulted in 77-140% inhibition of 3H-thymidine uptake by the 12th day of cultures in vitro in the three groups. These results suggest that BL/LL macrophages exhibit a premature inability to undergo tuftsin stimulated microbicidal activity, which may possibly be reversed by serial dosage of tuftsin.

Cu-Zn-superoxide dismutase activity in Moniezia expansa: inhibition by pyrimidine derivatives

Copper-zinc, cyanide-sensitive superoxide dismutase (Cu-Zn-SOD) was detected in homogenates of Moniezia expansa. The enzyme was purified by a sequence of multiple differential centrifugations, ammonium sulphate precipitation, ion-exchange and G-75 Sephadex column chromatography. The final enzyme preparation had a specific activity of 623.00 +/- 9.97U per mg protein and, after isolation, a single-staining band on acrylamide-SDS gels was detected which coincided with enzyme activity. The inhibitory activities of several benzimidazoles and several novel pyrimidine derivatives were determined on purified extracts of the M. expansa Cu-Zn-SOD. The results indicated that the percentage inhibition of Cu-Zn-SOD by some pyrimidine derivatives (6-amino-1, 3-dimethyl-5-nitroso-uracil, 6-amino-5-methyl-5-nitroso-uracil and 5-amino-uracil) was markedly higher than inhibition with the benzimidazoles.

Human phagocyte oxidative burst activation by BCG, M. leprae, and atypical mycobacteria: defective activation by M. leprae is not reversed by interferon gamma

The activation of the phagocyte oxidative respiratory burst by various mycobacteria was evaluated in an in vitro assay, by measuring the chemiluminescence, associated to the release of oxidizing species, generated by normal human whole blood phagocytes. All mycobacterium species, except Mycobacterium leprae, induced a significant chemiluminescence response. The strongest stimulus was provided by BCG, followed by M. triviale, M. chelonei, and M. fortuitum. M. kansasii, M. intracellulare, and M. lepraemurium elicited a weak response, although higher than that triggered by M. leprae. Both polymorphonuclear and mononuclear cells contributed to the whole blood cell chemiluminescence stimulated by mycobacteria, mononuclear cells being more efficient on a per cell basis. Phagocyte activation by recombinant interferon gamma did not improve M. leprae ability to trigger a significant chemiluminescence response. The failure of M. leprae and of some atypical mycobacteria to stimulate a strong phagocyte oxidative respiratory burst may have some relevance to their pathogenicity.

Reconstitution of murine resident peritoneal macrophages for antibody-dependent cellular cytotoxicity by homologous serum Clq

Mouse resident peritoneal macrophages (PM) were reconstituted in their response to activation for antibody-dependent cellular cytotoxicity (ADCC) for sheep erythrocyte targets (SRBC) by subhemolytic dilutions of homologous or autologous sera. ADCC-responsive inflammatory PM were largely unaffected in their activation by exogenous serum. Augmentation of resident PM for ADCC by homologous serum was correlated with the complement-activating potential of the mouse monoclonal anti-SRBC IgG isotype in that serum augmented IgG gamma 2a greater than IgG gamma 2b much greater than IgG gamma 1. The active component of mouse serum was heat-labile at 56 degrees C for 30 min and was present in both C5-deficient AKR and C5-sufficient homologous C3H mouse sera. Western blot analysis of the cell lysates for Clq confirmed that oil-elicited and thioglycollate-elicited inflammatory PM had greater levels of endogenous Clq than did resident PM which correlated with their innate responsiveness for ADCC activation. Depletion of Clq from serum by immunoprecipitation with IgG antibody to Clq or by ion exchange chromatography removed the active reconstituting activity for ADCC. Purified mouse Clq (0.4 microgram) partially replenished the ADCC augmenting activity of Clq-depleted AKR mouse serum. SRBC targets preopsonized with IgG gamma 2a and purified mouse Clq (0.075-5.0 microgram/ml) fully reconstituted the ADCC response of resident PM similar to homologous serum indicating that the major active component of serum was Clq. Thus resident PM with low endogenous levels of Clq were reconstituted for ADCC by the addition of exogenous Clq, whereas inflammatory PM with sufficiently high endogenous levels of Clq were not further enhanced by exogenous Clq. Our findings indicate that Clq may provide an essential second signal in concert with Fc receptor binding of IgG to initiate ADCC activation of macrophages.

Induced proteins in human peripheral mononuclear cells over a range of clinically tolerable doses of interferon-gamma

This study assessed biologic response modification at three different dose levels (0.15, 1.5, and 15 mg/m2) of interferon-gamma (IFN-gamma) administered by intravenous bolus three times weekly. A final total of 24 patients were evaluable. Dose-limiting toxicity occurred at the highest dose level (15 mg/m2) and included fatigue, leukopenia, and hepatotoxicity. Evaluation of biologic response modification included assessment of 2',5'-oligoadenylate (2-5A) synthetase activity in peripheral mononuclear cells, measurement of serum beta 2-microglobulin and expression of beta 2-microglobulin on monocytes, measurement of monocyte HLA Class II expression (HLA-DR, HLA-DQ), and measurement of hydrogen peroxide generation by monocytes 24 h after the first and fourth IFN-gamma treatments. Significant increases (p less than 0.05) from baseline were seen at 24 h with all parameters except H2O2 generation. Except for enhancement of HLA-DR, even the lowest dose (0.15 mg/m2) augmented synthesis of 2-5A synthetase and HLA proteins. A dose-response effect was noted for changes in serum and monocyte beta 2-microglobulin levels but not for 2-5A synthetase levels or HLA Class II antigen expression on monocytes. After 4 doses administered over 9 days, most parameters remained increased when compared to pretreatment, but were not further enhanced when compared with levels attained after the first dose. The results of this study document the efficacy of IFN-gamma for biological activation over a wide dose range and are consistent with the postulate that immunoregulatory effects of biological therapeutics can be obtained in man at doses substantially less than those that are maximally tolerated. Further documentation of biologic response parameters by IFN-gamma at low doses will be necessary to determine the importance of biologic activation in relation to antitumor activity.

Macrophage oxidative metabolism and intracellular Toxoplasma gondii

We explored the mechanisms by which Toxoplasma gondii avoids destruction by the oxidative metabolism of normal macrophages. Unelicited murine peritoneal macrophages were infected with T. gondii and exposed to different experimental conditions. As endpoints we used measurement of hydrogen peroxide (H2O2) release and intracellular reduction of nitroblue tetrazolium dye (NBT). Three main observations were made. Firstly, different T. gondii preparations (live or dead, opsonized or not) failed to trigger the respiratory burst. Combined challenges also showed that a primary T. gondii infection was able to block H2O2 release triggered by heat-killed (HK)-Candida albicans. The H2O2 release, however, once triggered by HK-C. albicans, was not inhibited by a subsequent challenge with T. gondii. Secondly, when a respiratory burst was obtained in T. gondii-infected macrophages--for instance by stimulation with phorbol myristate acetate (PMA)--the toxic oxygen metabolites (as determined by the NBT reduction test) did not seem to reach the vacuoles containing the parasite. Thirdly, when a respiratory burst occurred in T. gondii-infected macrophages, the intracellular development of T. gondii did not seem to be affected. In conclusion, we hypothesize that T. gondii is not damaged by the macrophage oxidative metabolism because the parasite fails to encounter toxic oxygen metabolites. The killing of intracellular T. gondii, as it is commonly observed in activated macrophages, does not appear oxygen-dependent.

Interferons and indoleamine 2,3-dioxygenase: role in antimicrobial and antitumor effects

Indoleamine 2,3-dioxygenase (IDO) is an interferon (IFN)-induced protein that initiates the metabolism of tryptophan along the kynurenine pathway. Although IDO can be induced by IFN-gamma in many cell types, only mononuclear phagocytes have been shown to be induced to decyclize tryptophan by all three IFN classes. Since tryptophan is an essential amino acid necessary for a variety of metabolic processes, depletion of available tryptophan may be an important mechanism for control of rapidly-dividing microbial pathogens and tumors. The purpose of this review is to present evidence that documents the effects of IFN-induced IDO on prokaryotic and eukaryotic pathogens, as well as on a variety of tumor cell lines.

Interferon-induced indoleamine 2,3-dioxygenase activity inhibits Chlamydia psittaci replication in human macrophages

Interferon-gamma (IFN-gamma) previously has been shown to inhibit the replication of Chlamydia psittaci in epithelial cells by inducing indoleamine 2,3-dioxygenase, the enzyme that decyclizes tryptophan to N-formylkynurenine. The role of indoleamine 2,3-dioxygenase in IFN-mediated inhibition of C. psittaci in human macrophages has now been examined. Peripheral blood monocytes from normal donors were isolated and cultivated 10-14 days to allow differentiation to macrophages. Cells were then treated with either IFN-gamma or IFN-beta for 48 h before infection with sufficient C. psittaci to infect approximately 30% of the cells. Infected cells were incubated 24 h, at which time coverslips were fixed, stained with Giemsa, and examined for development of C. psittaci inclusions by light microscopy. Complete inhibition of inclusion development was observed with IFN-gamma. In the absence of lipopolysaccharide, inhibition of C. psittaci by IFN-beta was variable; however, in the presence of lipopolysaccharide, IFN-beta also completely inhibited C. psittaci replication. The addition of excess tryptophan to the culture medium at the time of infection partially reversed the effect of IFN on the inhibition of C. psittaci growth in a concentration-dependent manner. Indoleamine 2,3-dioxygenase activity was determined by measurement of the concentrations of tryptophan and its metabolites in the culture medium after reversed-phase high-performance liquid chromatography. Significant indoleamine 2,3-dioxygenase activity was observed only in macrophages treated with IFN-gamma or combined IFN-beta plus lipopolysaccharide, and resulted in greater than 50% of available tryptophan being catabolized in a 4-h period.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitroblue tetrazolium reduction in monocytes and monocyte-derived macrophages. Effect of oxidative burst stimulants and interferons

The ability to mount an oxidative burst (OB) in response to medium, zymosan and phorbol myristate acetate (PMA) was assessed in human blood monocytes cultured for 1 day (MO) and monocyte-derived macrophages cultured for 10 days (MDM). Further, the effect of recombinant interferons (IFNs) on OB generation was examined. The OB was measured as a reduction of nitroblue tetrazolium (NBT). Unstimulated and stimulated NBT reduction per cell nucleus and the ratio of stimulated/unstimulated NBT reduction was not significantly different in cells cultured for 1 and 10 days. In MO, IFN-gamma stimulated the OB when co-stimulated with zymosan or PMA. IFN-alpha reduced MO adherence. When the lower adherence was corrected for, IFN-alpha enhanced NBT reduction. In MDM, a high concentration of IFN-gamma stimulated the OB without co-stimulation, in lower concentrations the presence of a co-stimulant was necessary for OB stimulation. IFN-alpha/beta enhanced the OB in response to PMA, suggesting that IFN-alpha/beta has a role in macrophage activation.

Evaluation of the causal relationship between crocidolite asbestos-induced lipid peroxidation and toxicity to macrophages

In vitro, crocidolite asbestos toxicity to macrophages is mediated by the production of reactive oxygen metabolites. We examined whether exposure of macrophages to crocidolite asbestos induced lipid peroxidation as measured by the thiobarbituric acid assay. When elicited mouse peritoneal macrophages were exposed to crocidolite, a dose- and time-dependent increase in lipid peroxidation breakdown products accompanied cell death. Superoxide dismutase plus catalase or deferoxamine prevented both lipid peroxidation and loss of viability caused by crocidolite. We tested whether crocidolite-induced lipid peroxidation was causally responsible for cell death. Macrophages were not killed by crocidolite when incubated with 10 mM 3-aminobenzamide. The level of thiobarbituric acid-reactive material was the same, however, for cells incubated with crocidolite in the presence or absence of 3-aminobenzamide. When macrophagaes were pretreated for 24 h with 25 microM vitamin E and then incubated with crocidolite, no thiobarbituric acid-reactive products were detected. Vitamin E, however, did not prevent crocidolite cytotoxicity. These results suggest that exposure of macrophages to crocidolite asbestos produces lipid peroxidation as measured by thiobarbituric acid-reactive products. This reaction, however, is not directly responsible for irreversible injury in this model system.

Differential induction of activation markers in macrophage cell lines by interferon-gamma

Macrophage cell lines were used in these studies as a model system to dissect the biochemical and functional mosaic of the macrophage activation process. In particular, the requirements for the induction of tumoricidal and bactericidal activity in the RAW 264.7 and WEHI-3 cell lines by interferon-gamma (IFN-gamma) and bacterial lipopolysaccharide (LPS) were determined. Changes in expression of a series of macrophage markers traditionally associated with macrophage activation were monitored during stimulation of the cells in order to determine whether a detectable pattern of activation-associated changes is associated with the development of a particular functional activity. These markers included changes in the cell surface expression of major histocompatibility complex-encoded Class I and Class II antigens and antigens in the Mac-1/LFA-1 family, alterations in the levels of membrane enzymes (5' nucleotidase and alkaline phosphodiesterase), and production of secretory products including hydrogen peroxide and the monokines interleukin-1, interferons-alpha/beta, and tumor necrosis factor-alpha. Our results demonstrate that a given homogeneous macrophage population expresses a distinct subset of functional activities in response to single, defined activating signals such as IFN-gamma and LPS. The display of a variety of macrophage surface antigens, enzymes, and secreted products is activated simultaneously by such treatment; however, the particular pattern of such activation-associated markers cannot reproducibly be used to predict the ability of an activated cell to perform a particular function. The results also suggest that macrophage cell lines expressing differential response patterns following IFN-gamma stimulation provide a valuable system for dissection of the molecular and cell biology of macrophage activation.

Is the conventional doctrine about macrophage activation still true?

The present results challenge the view that macrophage activation leads to a general, non-specific increase of microbicidal activity of these cells. Instead, it was found that the interactions between activated macrophages and micro-organisms are dependent on the kind of activation and the type of target micro-organism.

Cytochemical localization of plasma membrane enzyme markers during interiorization of tachyzoites of Toxoplasma gondii by macrophages

The enzyme activity of Mg++-ATPase, Na+-K+-ATPase, 5'-nucleotidase and NAD(P)H-oxidase was cytochemically detected at the ultrastructural level in mouse peritoneal macrophages infected with untreated and with specific antibody-coated Toxoplasma gondii tachyzoites. The Mg++-ATPase and 5'-nucleotidase were distributed throughout the macrophages' plasma membrane but were not observed in the membrane lining endocytic vacuoles containing ingested parasites; however, Na+-K+-ATPase activity was detected in the macrophages' plasma membrane as well as in the parasitophorous vacuoles that contained untreated or specific antibody-coated parasites. Reaction product, indicative of NAD(P)H-oxidase, was detected in the parasitophorous vacuoles that contained only specific antibody-coated parasites.

Effects of Histoplasma capsulatum on murine macrophage functions: inhibition of macrophage priming, oxidative burst, and antifungal activities

Histoplasma capsulatum yeast cells fail to trigger an oxidative burst response in normal murine macrophages. The results of this study, in which an in vitro assay of macrophage antifungal effects was used, extend these findings. During 18 h of incubation, unprimed elicited murine macrophages inhibited H. capsulatum growth only when macrophages were present in great excess. Gamma interferon (IFN-gamma)-primed macrophages showed enhanced fungal growth inhibition but a similar requirement for an excess of phagocytes. Macrophages containing heat-killed H. capsulatum exhibited diminished antifungal effects toward viable H. capsulatum and Saccharomyces cerevisiae cells. Parallel experiments showed no comparable effect of ingested latex particles on macrophage antifungal activity. Using chemiluminescence as a measure of the oxidative burst, we found that macrophages primed in vitro with IFN-gamma alone failed to exhibit a significant response to triggering by H. capsulatum yeast cells unless a second priming agent (tumor necrosis factor alpha or bacterial lipopolysaccharide) was added to IFN-gamma. Furthermore, macrophage priming with single agents was blocked by the prior ingestion of heat-killed H. capsulatum. These studies provide evidence that ingestion of H. capsulatum yeast cells can induce a prompt and enduring deactivation of murine macrophages.

Incorporation of recombinant gamma interferon into liposomes enhances its ability to induce peritoneal macrophage antitoxoplasma activity

In this study we compared the ability of free- and liposome-incorporated murine recombinant gamma interferon (rIFN-gamma) to enhance peritoneal macrophage H2O2 release and antitoxoplasma activity in vitro. rIFN-gamma was efficiently (37 to 47%) incorporated into multilamellar vesicles composed of phosphatidylglycerol/cholesterol in a 2:1 molar ratio. The amount of rIFN-gamma incorporated into multilamellar vesicles and added to macrophages (0.1 to 1,000 U/ml) was quantitated with [3H]rIFN-gamma. The concentration of liposomal rIFN-gamma required to enhance macrophage H2O2 release (1 U/ml) and maximally inhibit Toxoplasma gondii growth (10 U/ml) was one-tenth the concentration required for free rIFN-gamma (10 and 100 U/ml, respectively). This increase in potency was observed in both thioglycolate-elicited and resident peritoneal macrophages. Control liposomes containing encapsulated buffer had no effect on the potency of free rIFN-gamma. The duration of macrophage activation induced by 24 h of liposomal rIFN-gamma treatment was also considerably longer than that induced by free rIFN-gamma (2 days versus less than 1 day). These data indicate that liposomal rIFN-gamma is more active than free rIFN-gamma as an inducer of macrophage microbicidal properties in vitro. This enhanced activity, combined with the potential for selective delivery of liposomal rIFN-gamma to phagocytic cells in vivo, may improve the therapeutic efficacy of rIFN-gamma in infections characterized by parasitization of phagocytes.

The role of free oxygen radicals in the expulsion of primary infections of Nippostrongylus brasiliensis

The many and varied pathological, immunological and physiological manifestations of infection with Nippostrongylus brasiliensis may be unified by considering the role of leukocyte-generated free oxygen radicals in worm expulsion. Aside from directly damaging the adult stage of N.brasiliensis and possibly leading to its elimination from the small intestine, free radicals may also damage intestinal cells, thereby contributing to the gut pathology characteristic of infection. gamma-Interferon (and possibly tumour necrosis factor) may be involved in the initiation of free radical generation in response to N. brasiliensis and may also contribute to various side effects of infection such as hypertriglyceridaemia and cachexia. gamma-Interferon may initiate free radical generation via the agency of protein kinase C, an enzyme that can induce various additional responses including lysosomal enzyme and amine secretion and arachidonic acid metabolism. The possible interactions between these mediators and free radicals are subtle and diverse and may profoundly affect the course of infection.

Oxidative killing of intracellular parasites mediated by macrophages

An important function of macrophages is to eliminate invading pathogens, and one of their main weapons involves the generation of lethal oxygen radicals. Yet some parasites and pathogens - notably Leishmania, Toxoplasma, and Listeria and Mycobacterium - make use of macrophages as their primary cellular hosts displaying a capacity to survive the oxidative killing mechanisms of these host cells. It is now clear that more than one pathway is involved in the activation of macrophages to kill intracellular pathogens. Here, Huw Hughes discusses the biochemistry of the oxidative metabolism of macrophages, and the steps taken by parasites to survive within this hostile environment.

T lymphocyte responses to mycobacterial antigen in AIDS patients with disseminated Mycobacterium avium-Mycobacterium intracellulare infection

Patients with acquired immunodeficiency syndrome (AIDS) who have Mycobacterium avium-Mycobacterium intracellulare (MAI) infection typically have widely disseminated disease, often fail to respond to multi-drug chemotherapeutic regimens, and show little or no inflammatory tissue response. To determine if this clinicopathologic state correlates with in vitro lymphocyte responses to specific antigen, peripheral blood mononuclear cells from 18 patients with AIDS who had MAI bacillemia were stimulated with either particulate (heat-killed bacille Calmette Guérin [BCG]) or soluble (M intracellulare) mycobacterial antigens. In comparison to reactive cells from healthy control subjects testing positive with purified protein derivative of tuberculin (PPD) or from MAI-colonized (non-AIDS) control subjects, cells from 16 (89 percent) patients with AIDS essentially failed to show any antigen-induced proliferative activity or secretion of gamma-interferon; however, in two patients, antigen-stimulated proliferation of gamma-interferon production was modest but within the range of responses of normal healthy control subjects. Thus, although an occasional patient with AIDS can develop disseminated MAI infection despite the presence of antigen-reactive cells in vitro, most MAI-infected patients with AIDS display a striking defect in responsiveness to both particulate and soluble mycobacterial antigens. Since treatment with gamma-interferon activates the mononuclear phagocyte in vivo, these results suggest a rationale for a trial of gamma-interferon therapy in patients with AIDS who have disseminated MAI infection.

Interferon-gamma: the major mediator of resistance against Toxoplasma gondii

Mice were injected with a monoclonal antibody to interferon-gamma to examine the importance of endogenous production of this lymphokine in resistance against infection with the sporozoan parasite Toxoplasma gondii. Mice with intraperitoneal infections of T. gondii that received no antibody survived and developed chronic T. gondii infection, whereas the infected mice that received the monoclonal antibody died of toxoplasmosis. The activation of macrophages, which kill T. gondii in vivo, was inhibited by administration of the monoclonal antibody, but the production of antibodies to T. gondii was not suppressed. The fact that an antibody to interferon-gamma can eliminate resistance to acute Toxoplasma infection in mice suggests that this lymphokine is an important mediator of host resistance to this parasite.

Macrophage activity in resistant and susceptible mouse strains infected with Mycobacterium lepraemurium

The level of activation of peritoneal macrophages following subcutaneous inoculation of resistant (C57BL) and susceptible (BALB/c) mice was assessed by monitoring superoxide anion and hydrogen peroxide production and also tumour cell cytostasis. The level of systemic macrophage activation appeared to correlate with bacterial load, rather than resistance to infection. It was observed that the more susceptible (BALB/c) strain developed higher and more sustained levels of systemic macrophage activation, whereas the more resistant (C57BL) strain showed only low transient levels of macrophage activation. In contrast, in vivo challenge of subcutaneously infected C57BL mice, via the intra-peritoneal route, with heat-killed Mycobacterium lepraemurium and thioglycollate resulted in a high level of macrophage activation compared with similarly treated uninfected mice. Similar treatment of susceptible BALB/c mice, however, did not result in enhanced macrophage activation. It was also observed that high levels of macrophage activation occurred in T-cell deprived C57BL mice following infection with M. lepraemurium.

Roles of factor increasing monocytopoiesis (FIM) and macrophage activation in host resistance to Listeria monocytogenes

The present contribution concerns two aspects of host resistance in overcoming an infection with Listeria monocytogenes. One of these aspects is the regulation of monocyte production by the factor increasing monocytopoiesis (FIM), a macrophage-derived factor. Listeria-resistant (C57BL/10 mice and Listeria-sensitive CBA mice produce and secrete similar amounts of FIM in response to an inflammation induced by soluble Listeria antigen. However, monocyte precursors in the bone marrow of Listeria-resistant mice react to an injection of serum containing FIM by increased monocyte production, whereas Listeria-sensitive mice are unable to react to this stimulus. The other aspect of host resistance to L. monocytogenes is the activation of macrophages leading to increased bactericidal activity. Macrophages of both mouse strains stimulated first with live BCG and then with PPD, killed ingested Listeria faster than resident peritoneal macrophages did. However, recombinant interferon-gamma, thought to be the most important macrophage-activating factor, did not induce increased listericidal activity in macrophages.

Suppression of yeast ingestion by dexamethasone in macrophage cultures: evidence for a steroid-induced phagocytosis inhibitory protein

The mechanism by which glucocorticoid steroids suppress yeast phagocytosis in cultures of resident and thioglycollate-elicited murine peritoneal macrophages was examined. Time course and dose-response studies demonstrated that the phagocytic capacity of resident macrophages was suppressed by dexamethasone to the same extent in both newly established cultures and cultures that were incubated for several days. In contrast, relative to newly established cultures of elicited cells that were treated with the drug, elicited macrophages that were incubated for at least 1 day prior to exposure to dexamethasone, exhibited enhanced sensitivity to the action of the steroid. Steroid-induced phagocytic inhibitory responses were blocked by the metabolic inhibitors cycloheximide and actinomycin D. The suppression of phagocytosis by dexamethasone was mediated by a factor, present in the cellular homogenates of steroid-treated macrophages, that was partially purified by Sephadex G-25 chromatography. Since the phagocytic inhibitory activity in these homogenates was destroyed following exposure to heat and trypsin, the factor has been named phagocytosis inhibitory protein (PIP). The antiphagocytic activity of PIP was neutralized by treatment with RM23, a monoclonal antibody directed against lipocortin. The results support the hypothesis that the suppression of yeast ingestion is mediated by the action of PIP, which is induced in dexamethasone-treated macrophage cultures. Moreover, PIP appears to belong to the lipocortin family of phospholipase inhibitory proteins.

Interactions of Mycobacterium lepraemurium with resident peritoneal macrophages; phagocytosis and stimulation of the oxidative burst

Live Mycobacterium lepraemurium or 60Co-gamma-irradiated organisms stimulated a very weak oxidative burst compared with similar numbers of heat-killed organisms or with live M. microti. This was found to reflect the poor uptake of the living organisms rather than an absolute failure to stimulate an oxidative burst. It is possible, however, that phagocytosis of fewer than 3-4 bacteria may not trigger the respiratory burst. Pre-incubating live M. lepraemurium with sera from infected mice, but not with fresh normal mouse sera, resulted in enhanced phagocytosis with a concomitant increase in the oxidative burst. The level of opsonic activity correlated with the M. lepraemurium specific antibody titres. The opsonic activity appeared to be mediated by antigen-antibody activation of the classical complement pathway as heat-inactivation destroyed the activity.

Stimulation of macrophage H2O2 release by resident thymocytes: effect of a soluble factor distinct from interferon-gamma

Activated T cells are known to stimulate macrophage oxidative metabolism and antimicrobial activity through release of interferon-gamma (IFN-gamma). In contrast, the role of nonactivated T cells in regulating macrophage effector functions is less well defined. We have previously reported that a low molecular weight soluble factor derived from resident (nonactivated) thymocytes enhances macrophage receptor-mediated phagocytosis. In the present study, we examined the capacity of resident murine thymocytes to stimulate the respiratory burst and microbicidal activity of peritoneal macrophages. Macrophages cultured for 1-2 days with cell-free thymocyte supernatant (TS) released two to three times more H2O2 in response to PMA or opsonized zymosan than did control macrophages. The H2O2-stimulating factor in TS was distinguished from IFN-gamma by its heat stability (100 degrees C, 20 min), approximate MW of 2400 Da (gel filtration high-pressure liquid chromatography), and absence of interferon activity in both antiviral and enzyme-linked immunosorbent assays. TS-treated macrophages, however, did not exhibit a greater capacity to kill or inhibit the intracellular growth of Toxoplasma gondii, indicating that the thymocyte factor did not fully activate macrophage microbicidal mechanisms. These data suggest that thymocytes can increase the respiratory burst capacity of macrophages in the absence of antigen-specific immune responses.

Induction of synthesis of components of the hydrogen peroxide-generating oxidase during activation of the human monocytic cell line U937 by interferon-gamma

Increased amounts of cytochrome b-245 and a 45 kDa polypeptide component of the hydrogen peroxide-generating oxidase were detected in the human monocytic cell line U937 after incubation in interferon-gamma. The time course of increase in cytochrome b-245 paralleled the induction of oxidase activity. Induction of the 45 kDa component had a different time course, having a greater lag before increased amounts were seen.

Alveolar macrophage dysfunction in systemic lupus erythematosus

A high frequency of pulmonary infections has been a well-described feature of systemic lupus erythematosus (SLE). Alveolar macrophages (AM) play a crucial role in pulmonary bacterial defense. We therefore examined the antibacterial activity of AM and generation of superoxide anion in 17 patients with SLE without clinical or radiologic pulmonary changes and in 8 control subjects. Total cell count and cellular viability of AM (trypan blue exclusion) did not differ significantly between patients and control subjects. Antibacterial activity v/s Staphylococcus aureus was significantly decreased in both untreated and corticosteroid-treated patients (respectively, -16.2 +/- 7.4 and -42 +/- 12% compared with the normal value of 51 +/- 12%, p less than 0.001). The defect of antibacterial activity was observed as well v/s S. aureus as v/s Escherichia coli. In contrast, chemiluminescence response of AM before and after stimulation by either phorbol myristate acetate or opsonized zymosan did not differ among control subjects and treated and untreated patients with SLE. We did not find any correlation between disease activity and AM function. Antibacterial activity of normal AM was shown to be significantly reduced by previous incubation with SLE serum compared with normal human serum. Thus, our findings suggest that alteration of antibacterial activity of AM may contribute to the increased susceptibility to lung infections observed in SLE.

Comparative oxidative microbicidal activity of human blood monocytes and alveolar macrophages and activation by recombinant gamma interferon

The relative oxidative and microbicidal activities of human blood monocytes compared with those of alveolar macrophages (AM) are poorly defined. Furthermore, the comparative efficiency of recombinant gamma interferon (rIFN gamma) to enhance microbicidal function of these 2 cell populations is uncertain. In this study, blood monocytes and AM were obtained concomitantly from 10 healthy, nonsmoking human subjects. Cells were adjusted to equivalent cell concentrations and assayed for respiratory burst activity (superoxide anion production) during soluble (Concanavalin A) or particulate (bacteria) stimulation. Microbicidal activity against Pseudomonas aeruginosa, Listeria monocytogenes, and Candida albicans was also determined for each cell type. Finally, the capacity of rIFN gamma treatment (200 U/ml for 24 h) to enhance these cellular activities was determined. Oxidative activity of AM was greater than that of blood monocytes (p less than 0.01, bacteria; p less than 0.02, Con A). Likewise, AM exhibited greater killing of P. aeruginosa (p less than 0.01) and L. monocytogenes (p less than 0.01) than did monocytes. Neither cell killed C. albicans. Treatment with rIFN gamma greatly enhanced both respiratory burst and microbicidal activity of blood monocytes, but had no effect on AM respiratory burst. Despite this, rIFN gamma-treated AM did exhibit some enhanced killing of L. monocytogenes (p less than 0.05). We conclude that oxidative microbicidal activity of resident AM greatly exceeds that of blood monocytes, but that blood monocytes are relatively more susceptible to activation by rIFN gamma.

Correlation between release of reactive oxygen intermediates and inhibition of Toxoplasma multiplication in mouse peritoneal and alveolar macrophages and kidney cells after in vitro incubation with Obioactin, lonomycin A, muramyl dipeptide, lipopolysaccharide or Toxoplasma lysate antigen

The inhibition of Toxoplasma multiplication inside cells does not correlate with an enhanced release of oxygen intermediates except in the case of peritoneal macrophages treated with Obioactin. The inhibition observed in alveolar macrophages treated with Obioactin, in kidney cells treated with Obioactin or lonomycin A and in peritoneal macrophages treated with lonomycin A was not accompanied by an increment of release of oxygen intermediates. Lipopolysaccharide (LPS) and muramyl dipeptide (MDP) enhanced the release of toxic oxygen intermediates in peritoneal macrophages, but did not have any toxoplasmacidal effect. Adenosine triphosphate (ATP) content increased during Obioactin, MDP or Toxoplasma lysate antigen (TLA) treatment. The actual oxygen consumption of the peritoneal macrophages treated with Obioactin increased dose dependently, but that of TLA-, lonomycin A- or MDP-treated cells did not change. These results suggest that the relationship between the intracellular killing of Toxoplasma protozoa and the release of oxygen intermediates differs according to the cells and/or the stimuli, and that the cellular mechanism of Toxoplasma killing in the peritoneal macrophages treated with Obioactin involves an energy-dependent mechanism.

Study of DTH and resistance in Mycobacterium lepraemurium infection using a T-cell line isolated from mice infected with Mycobacterium bovis (BCG)

A T-cell line of mixed phenotype (60% L3T4+, 40% Lyt-2+) was isolated from mice infected with Mycobacterium bovis (BCG). This line responded to M. lepraemurium and BCG but not to M. leprae and produced TCGF spontaneously. It also produced factors which stimulated macrophages to secrete hydrogen peroxide and superoxide anion. In vivo studies showed that only L3T4+ cells were required to transfer DTH responses and that Lyt-2+ cells suppressed this response. Both L3T4+ and Lyt-2+ cells were required to inhibit M. lepraemurium multiplication in vivo.

Enhancement of production of superoxide anion by human monocytes exposed to products of HT 29 human colonic adenocarcinoma cell line

The generation of superoxide anion (O2-) by human blood monocytes in response to stimulation by either phorbol myristate acetate (PMA) or opsonized Zymosan was greatly enhanced (range: 100-200% according to donor) by prior exposure of the peripheral blood mononuclear cells (PBM) to human colonic adenocarcinoma cells (HT 29 line) or their conditioned culture medium (DMEM-HT 29). This priming effect was observed after 5 hr and persisted for up to 15 hr of contact between PBM and endotoxin-free DMEM-HT 29. Beyond this time, primed monocytes gradually lost this ability. However, they maintained a higher capacity (about 100%) to produce O2- when compared to controls. DMEM-HT 29-induced monocyte priming requires that the tumor-active substance(s) act(s) on 2 target cells: first, on non adherent mononuclear cells (NA-PBM) to induce cytokine production and, second, on the monocyte itself. Priming activity was also found in conditioned medium from FR3T3 embryonic fibroblasts but not in conditioned medium from HT 29 repolarized cells (by culture in glucose-free medium) or from non-tumorous human colonic mucosa explants.

Effect of lipopolysaccharide on intracellular killing of Leishmania enriettii and correlation with macrophage oxidative metabolism

The effect of lipopolysaccharide (LPS) on the lymphokine (LK)-dependent activation of murine peritoneal macrophages for intracellular killing of Leishmania enriettii parasites was investigated. Exposure to LPS alone did not induce macrophages to kill the parasite. In the presence of LK or recombinant interferon-gamma, however, which by themselves rendered the macrophages only weakly cytotoxic, considerable stimulation of intracellular parasite killing was achieved already at a LPS concentration of 1 ng/ml. The response to LPS was of the same magnitude in macrophages tested for intracellular killing as in parallel assays of extracellular cytolysis of target cells. Acquisition of leishmanicidal activity by macrophages exposed to LK and LPS correlated with stimulation of the respiratory burst, as shown by increased hexose monophosphate shunt levels, and priming for elevated chemiluminescence and O2- and H2O2 production. Polymyxin B blocked both this LPS-dependent metabolic activity and intracellular parasite destruction. Intracellular killing was, however, not solely dependent on oxidative metabolism of macrophages since in the absence of LK, LPS stimulated respiratory burst activity, yet no intracellular killing was observed, and triggering of the respiratory burst by phorbol myristate acetate or zymosan did not affect intracellular parasite survival. These results suggest that, in this experimental model, efficient intracellular parasite killing depends both on increased production of oxygen metabolites and on the availability of so far unidentified factor(s), the synthesis of which requires exposure of macrophages to both LK and LPS.

Histoplasma capsulatum fails to trigger release of superoxide from macrophages

The yeast form of the dimorphic fungus Histoplasma capsulatum survives within macrophages after phagocytosis. To do so, it must avoid, inhibit, or resist a variety of toxic oxygen metabolites. Using ferricytochrome c reduction to assay superoxide release, we examined the response of mouse macrophages to the yeast form of various H. capsulatum strains. Doses of zymosan as low as 20 particles per macrophage elicited superoxide, whereas H. capsulatum failed to induce superoxide even at 160 yeast cells per macrophage. This phenomenon was observed with two virulent strains of H. capsulatum (G217B and G186A) and with an avirulent variant of G186A. Over a 15- to 150-min observation period, zymosan stimulated increasing reduction of ferricytochrome c, but H. capsulatum did not. When added concurrently with zymosan, H. capsulatum had no effect on superoxide production. Therefore, H. capsulatum was unable either to inactivate the oxygen radical or inhibit host cell superoxide response to other competent stimuli. Enzymatically generated superoxide reduced ferricytochrome c even in the presence of H. capsulatum, again implying that the organism does not readily inactivate superoxide. This experiment also demonstrated that the yeast did not interfere with the assay used. Thus, rather than inhibiting superoxide generation or inactivating the anion, H. capsulatum yeast cells appear to avoid the toxic effects of superoxide by failing to trigger its release.

Induction of tryptophan catabolism is the mechanism for gamma-interferon-mediated inhibition of intracellular Chlamydia psittaci replication in T24 cells

Human uroepithelial (T24) cells were incubated for 24 h in the presence of various concentrations of human recombinant gamma interferon (Hu-rIFN-gamma) and then infected with the 6BC strain of Chlamydia psittaci. This resulted in a reduction of intracellular chlamydial inclusion development in proportion to the concentration of Hu-rIFN-gamma present when Giemsa-stained cells were examined by light microscopy 24 h after infection. When tryptophan was added to Hu-rIFN-gamma-treated cells just after infection, reversal of the Hu-rIFN-gamma-mediated inhibition occurred in proportion to the concentration of tryptophan added. Addition of either isoleucine or lysine did not result in reversal of the antichlamydial state. Transport of L-[3H]tryptophan into acid-soluble intracellular pools was found to be greatly enhanced in Hu-rIFN-gamma-treated T24 cells compared with the rates measured for untreated cells. Transport of [3H]leucine was not increased in treated cells. Cells treated with Hu-rIFN-gamma also degraded L-[3H]tryptophan to catabolites that cochromatographed with N-formylkynurenine and kynurenine as measured by high-performance liquid chromatography. We conclude that Hu-rIFN-gamma-mediated inhibition of intracellular C. psittaci replication in T24 cells occurs by depletion of the essential amino acid tryptophan, most likely via the induction of indoleamine-2,3-dioxygenase, the initial enzyme of tryptophan catabolism.