Innate immune properties of the immortalized macrophage cell line I-9.5.

A colony stimulating factor-1-dependent macrophage cell line, I-9.5, originally derived from a BALB/c splenic macrophage colony, was maintained in culture and examined for the expression of certain properties key to its innate immune function. Chemotaxis, phagocytosis, and superoxide release were assessed in this cell line and compared to either freshly isolated elicited murine peritoneal or splenic macrophages from BALB/c mice. Three separate experiments indicated that I-9.5 displayed comparable phagocytosis of 14C-radio-labeled Staphylococcus aureus and similar levels of superoxide release in response to opsonized zymosan. I-9.5, however, demonstrated impaired chemotaxis toward the chemoattractant, N-formyl-methionyl-leucyl-phenylalanine, and displayed impaired random migration in response to a balanced salt solution. This observation suggests that I-9.5 may serve as an important model for elucidating the structural and molecular correlates of chemotaxis.

Activation of a distinct subpopulation of pulmonary macrophages following exposure to biological response modifiers.

A distinct subpopulation of tissue-associated pulmonary macrophages (TAPM) displayed tumoricidal activity towards syngeneic and xenogeneic targets following in vitro incubation with N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP). This subpopulation, as well as, the predominant population of freely lavagable alveolar macrophages destroyed allogeneic targets following a similar incubation with either 6-0-stearoyl MDP (S-MDP) or recombinant interferon-gamma (IFN-gamma). IFN-gamma-induced in vivo tumoricidal activation of both populations of pulmonary macrophage was most effective when delivered either intravenously or via osmotic minipump infusion and least effective when administered by direct intratracheal instillation. The separate populations also displayed in vivo activation in response to liposome-encapsulated i.v. administered S-MDP. Under comparable conditions, IFN-alpha was not nearly as effective. Metabolic activation of TAPM, assessed by the release of increased levels of superoxide free radicals during phagocytosis, occurred following 24 hr exposure to S-MDP or lipopolysaccharide. Incorporation of these agents into multilamellar vesicle liposomes further augmented the release of superoxide observed at 24 hrs. Our results collectively demonstrated that a subpopulation of lung macrophage, a tissue-associated pulmonary macrophage, may be activated to a tumoricidal state and to release pronounced levels of oxygen free radicals following either in vitro or in situ treatment with several biological response modifiers.

Inflammatory cell function in young rodents with experimental cholestasis: investigations of functional deficits, their etiology, and their reversibility.

Children with cholestasis are susceptible to infective complications. This may be attributable to impaired host defense. We postulated that cholestasis affects systemic polymorphonuclear leukocyte (PMN) function by impeding chemotaxis, phagocytosis, and superoxide release, which are all critical in eliciting an adequate immune response. Sprague Dawley rats (225 g) were assigned to three groups: bile duct ligated (BDL), sham (SH), and normal control (NC). On day 21 after operation, PMN and sera were isolated. Chemotactic response to C5a and FMLP (formyl-methionyl-leucyl-phenylalanine), superoxide release, and phagocytic uptake of 14C-labeled Staphylococcus aureus were performed on pooled PMN samples. Results were expressed as mean +/- SD. Serum bilirubin at day 21 was 6.3 +/- 2.9 v 0.1 +/- 0.1 and 0.1 +/- 0 mg/dL (P less than .01) in BDL, SH, and NC groups, respectively. Kinetic studies of PMN phagocytosis demonstrated impaired 14C S aureus uptake by BDL neutrophils at 60 (P less than .05), 90 (P less than .05), and 120 minutes (P less than .05) compared with SH and NC groups. No differences in PMN chemotactic response to C5a and FMLP was observed in BDL, SH and NC groups (43 +/- 14 v 40 +/- 12 and 33 +/- 1, and 43 +/- 20 v 43 +/- 14 and 28 +/- 1 cell per field, respectively). Zymosan stimulated superoxide release did not differ between groups (14.3 +/- 3.6 (BDL) v 15.1 +/- 8.7 (SH) and 12 +/- 2.0 (NC) nmol/30 min/mg cell protein, respectively. Thus, cholestasis impairs neutrophil phagocytosis in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-2 protects neonatal mice from lethal herpes simplex virus infection: a macrophage-mediated, gamma interferon-induced mechanism.

Administration of human recombinant interleukin-2 (IL-2) protected neonatal mice from a lethal herpes simplex virus (HSV) infection. Protection was not associated with viral antibody production, enhanced natural killer cell cytotoxicity, or intrinsic resistance of macrophages to viral infection. Protection was associated with increased macrophage-mediated antiviral antibody-dependent cellular cytotoxicity (ADCC). Spleen cells from IL-2-treated neonatal mice and from neonatal mice that were treated in vitro with IL-2 transferred protection to neonatal mice. These cells, by adherence, silica, and asialo GM 1 antibody treatment, were shown to be macrophages. IL-2 treatment in vitro enhanced the neonatal macrophages' ADCC function and superoxide release. Similar protection was induced by gamma interferon (IFN-gamma)-treated spleen cells. Antibody to IFN-gamma ablated both IFN-gamma- and IL-2-induced protection by adherent spleen cells. Thus, IL-2-mediated protection against murine neonatal HSV infection was affected by stimulated macrophage activity, via helper T cell-produced IFN-gamma.

Impaired nonspecific cellular immunity in experimental cholestasis.

The abilities of polymorphonuclear leukocytes (PMN) and pulmonary alveolar macrophages (PAM), to demonstrate chemotaxis, phagocytosis, and superoxide release after bile duct ligation in the rat were investigated to determine the effect of cholestasis on nonspecific cellular immune mechanisms. Chemotactic response to C5a and FMLP, phagocytosis of 14C labeled Staphylococcus aureus, and zymosan-induced superoxide release were evaluated 21 days after bile duct ligation (BDL), sham operation, or in normal controls. Serum total bilirubin level was elevated after BDL (p less than 0.01). Chemotactic ability was similar to each group. PMN phagocytic uptake of 14C labeled Staphylococcus aureus was depressed in BDL (p less than 0.05). BDL rats exhibited impaired PAM phagocytic indices and improved PMN superoxide release (p less than 0.03). PAM superoxide release was similar in each study group. Alterations in phagocytic function with cholestasis are important deficits in nonspecific cellular immunity that may contribute to the high incidence of infective complications associated with obstructive jaundice.

Evidence of an immune system to brain communication axis that affects central opioid functions: muramyl peptides attenuate opiate withdrawal.

Muramyl peptides are metabolic breakdown products of bacterial cell walls formed in vivo by the reticuloendothelial system. These agents have a variety of immune modulatory and neuropharmacologic effects. It has previously been demonstrated that a variety of immune modifying agents can induce alterations in certain behaviors elicited by opiates. In the present study we investigate possible reciprocal interactions between muramyl dipeptides (MDPs) and central opioid systems using three different experimental models: (1) naloxone-precipitated withdrawal behavior in morphine-dependent rats; (2) the tail immersion assay for determination of morphine-induced antinociception and (3) rectal temperature measurement of the pyrogenic activity of MDP. It is shown that two derivatives of MDP attenuate the severity of naloxone-precipitated withdrawal and morphine-induced antinociception. In addition, it is demonstrated that the pyrogenic activity of a stearoyl derivative of MDP is altered by chronic morphine treatment. These findings suggest both novel neuropharmacologic properties of muramyl dipeptides, as well as demonstrate that yet another immune modifier interacts with centrally mediated opioid phenomena.

Evidence of neuro-immunologic interactions: cyclosporine modifies opiate withdrawal by effects on the brain and immune components.

The capacity of the immune system to participate in processes primarily considered to be central nervous system (CNS) phenomena has been suggested recently by several studies demonstrating the ability of various immune modifiers to attenuate opiate withdrawal severity. The present study demonstrates that within 2 h after injection, the immune modifier cyclosporine A (CsA) has the ability to attenuate the opiate withdrawal syndrome precipitated by naloxone in morphine-dependent animals. Furthermore, it is demonstrated that this effect of CsA can be adoptively transferred by splenic mononuclear cells from immune-modulated (CsA-treated) donors into morphine-dependent recipients. However, unlike direct injections of CsA, CsA-treated immune components require at least 24 h to achieve their full attenuating effect upon withdrawal severity. Since opiate withdrawal behavior is predominantly a CNS-mediated phenomenon, these observations suggest both direct effects of CsA on the brain as well as the participation of immune components in the opiate withdrawal syndrome. This finding lends further support to the hypothesis that immune components have the ability to modulate central nervous system activities in a neuro-immunologic axis of communication.

Modulation of pulmonary macrophage superoxide release and tumoricidal activity following activation by biological response modifiers.

Following immunologic activation, pulmonary macrophages may prevent or cause regression of lung metastases by mechanisms which remain largely unknown. The studies described here were designed to determine if enhanced oxygen metabolite release was related to postactivation tumoricidal activity. We have shown that in vitro activation of Fischer 344 rat pulmonary macrophages by either free or liposome-encapsulated muramyl dipeptide leads to both enhanced release of superoxide anions and marked tumoricidal activity against syngenic (Fischer 13762), allogeneic (Schmidt-Ruppin RR 1022) and xenogeneic (Fibrosarcoma MCA-F) 125I-deoxyuridine-labeled target cells. This immune modulator did not, however, metabolically activate pulmonary macrophages as effectively as liposome-encapsulated lipopolysaccharide. A 24-h in vitro incubation with either 150 U or 300 U of interferon-gamma (3 X 10(6) U/mg) or 30 U, 150 U or 300 U of interferon-alpha (6 X 10(5) U/mg) caused a significant elevation in superoxide release above controls, whereas short-term exposure (2 or 4 h) had little or no effect. Free or encapsulated 6-O-stearoyl muramyl dipeptide, on the other hand, did increase superoxide levels at all 3 time periods. When either interferon-gamma or free or encapsulated muramyl dipeptide derivative were administered to intact rats by either i.v. injection, intratracheal instillation or osmotic minipump infusion, pulmonary macrophage tumoricidal activity was observed 96 h after cell harvesting. Zymosan-stimulated superoxide release, however, was not consistently elevated above control or empty liposome treatment following this course of in vivo activation. The data collectively suggest that in vivo pulmonary macrophage activation to a tumoricidal state and metabolic activation resulting in enhanced superoxide may be separable events.

Influence of dietary nucleotide restriction on bacterial sepsis and phagocytic cell function in mice.

Although enzyme defects in purine metabolism have revealed the importance of these substrates to maintenance of a normal immune response, the role of exogenous nucleotides on the cells that mediate the host defense system has remained largely unexplored. Recent investigations have revealed that dietary nucleotides are vital to the maintenance of cell-mediated responses to antigen stimulation. To test the influence of dietary nucleotide deprivation on resistance to infection, Balb/c mice were maintained on chow, a nucleotide-free (NF) diet, or an NF diet repleted with adenine, uracil, or RNA. Mice on the NF diet suffered 100% mortality following intravenous challenge with Staphylococcus aureus, while chow-fed and RNA- or uracil-repleted mice demonstrated significantly greater resistance to this bacterial challenge. Macrophages from mice on the NF diet had decreased phagocytic activity as measured by uptake of radiolabeled bacteria compared with mice maintained on the NF diet supplemented with adenine, uracil, or RNA. No change in S aureus antibody response was noted on the various diets. Although the mechanism of this suppression of nonspecific immunity remains unclear, provision of nucleotides to defined diets appears vital to maintain host resistance to bacterial challenge.

Enhanced superoxide release and tumoricidal activity by a postlavage, in situ pulmonary macrophage population in response to activation by Mycobacterium bovis BCG exposure.

The monocytic phagocyte population of rat lungs is heterogeneous. In addition to the freely lavagable alveolar macrophages, there is a fixed in situ tissue-associated subpopulation of pulmonary macrophages. The response of this subpopulation to classical macrophage activation by Mycobacterium bovis BCG exposure was monitored. Results indicate that this population can be activated both metabolically and functionally, as evidenced by enhanced release of superoxide anions and demonstrable tumoricidal activity against syngeneic and xenogeneic target cells. The pattern of metabolic activation of in situ tissue-associated macrophages differed somewhat from that of alveolar macrophages and was observed only after subsequent exposure of the cells to either zymosan particles or phorbol myristate acetate. Upon such exposure, the activated zymosan-treated tissue macrophages released approximately twice as much superoxide as the nonactivated cells and amounts comparable to the amounts released by activated alveolar macrophages. The tissue macrophages also displayed greater levels of cytotoxicity toward xenogenic targets than the alveolar cells and may have an important role in preventing microbial or tumor cell colonization of respiratory systems.

Cyclosporine alters opiate withdrawal in rodents.

Opiates exert numerous effects on all levels of the central nervous system with tolerance, physical dependence and withdrawal being characteristics of this drug class. The degree of dependence is directly correlated to the intensity of withdrawal. Therefore, success in modifying the withdrawal syndrome may shed light on the dynamics of opiate addiction. The present study demonstrates that cyclosporine, a widely used immunosuppressive drug, considerably modified the behavioral signs of a naloxone-induced abstinence syndrome in morphine-addicted rats. In previous experiments, alpha-interferon has shown similar results. The similarity in actions of these two immunomodulator drugs is discussed and we suggest that opiate addiction may involve the immune system.

Mechanism of HgCl2 cytotoxicity in cultured mammalian cells.

Treatment of intact Chinese hamster ovary cells with HgCl2 produced a rapid, concentration-dependent induction of DNA single-strand breaks (SSB) as revealed by alkaline elution analysis. Direct addition of HgCl2 to cell lysates did not result in DNA strand breaks. HgCl2 treatment of cells also caused a rapid leakage of superoxide radicals that were detected in their media by measurement of the reduction of exogenously added cytochrome c. There was a linear relationship between the production of radicals and the induction of DNA strand breaks, and there were also excellent temporal correlations in these parameters. Addition of oxygen radical scavengers, such as the enzymes superoxide dismutase and catalase, to the extracellular media significantly reduced the extent of DNA damage caused by HgCl2 without a similar attenuation of its uptake into cells, as did the autoclaved enzymes. Similarly, addition of radical scavengers such as glycerol or ascorbate inhibited the DNA damage but also reduced the uptake of the metal by almost the same degree. Thus, because of secondary effects on uptake of the metal, the radical scavenger experiments could not address the importance of oxygen radicals in the DNA damage caused by HgCl2. SSB were enhanced when cells were treated with HgCl2 and diethylmaleate or diethyldithiocarbamate, agents that deplete cellular reduced glutathione or inhibit the intracellular activity of superoxide dismutase, respectively. Thus, DNA damage in cells rendered sensitive to radicals was greater when these cultures were subsequently treated with HgCl2. The binding of 203HgCl2 to the DNA of intact Chinese hamster ovary cells was also studied. These studies were made possible by the relatively high stability of Hg(II) interaction with DNA and by utilizing a gentle method of DNA isolation that minimized redistribution of intracellular Hg(II) complexes after cells were lysed. The amount of Hg(II) bound to DNA varied from approximately 7 to 35 Hg atoms per 10(4) base pairs (bp) at concentrations of HgCl2 that have been previously shown to produce between 1 SSB/10(7) bp and 1 SSB/10(6) bp. The Hg(II)-DNA adducts were relatively stable complexes, since they resisted treatment with 0.1 M EDTA and 1 M NaCl and were stable to precipitation of the DNA with ethanol and trichloroacetic acid. However, the Hg(II) was released from the DNA when it was degraded enzymatically to mononucleosides, suggesting that the Hg(II)-DNA bonds formed in the cell were not truly covalent and that the strength of Hg(II) binding to DNA depended upon polynucleotide structure.(ABSTRACT TRUNCATED AT 400 WORDS)

Phagocytic cell function in response to immunosuppressive therapy.

The increased incidence of pulmonary infection in human renal allograft recipients is presumably related to antirejection immunosuppressive therapy. To assess immunosuppressive-related disturbances of the immune responses of the lung, we evaluated the functional abilities of the pulmonary alveolar macrophage (PAM) and polymorphonuclear leukocyte (PMN) of rats in chemotaxis, phagocytosis, and superoxide-release assays following 30 days of intraperitoneal administration of cyclosporine, azathioprine, and/or prednisolone sodium succinate. None of these drugs affected superoxide release by stimulated PAMs or PMNs. Except for a transient inhibition by azathioprine, the drugs had no effect on phagocytosis of Staphylococcus aureus by either cell type. On the other hand, cyclosporine inhibited formyl-methionyl-leucyl-phenylalanine (FMLP)-directed chemotaxis by PAMs, and both FMLP and C5a stimulated chemotaxis by PMNs. Azathioprine had more dramatic effects on PAMs than on PMNs and prednisolone at 2 mg/kg inhibited PAMs. The results indicated that, with the exception of chemotaxis, the immunosuppressive agents largely spare nonspecific elements of host defense.

Alterations in rat pulmonary macrophage function by the immunosuppressive agents cyclosporine, azathioprine, and prednisolone.

Disturbances of the immune response of the lung induced by the action of immunosuppressive agents on the functional abilities of rat pulmonary alveolar macrophages (PAM) were analyzed following in vitro incubation or in vivo administration (for 30 days) of cyclosporinea, (CsA) azathioprine (Az) or prednisolone (Pr). Two major parameters were analyzed: oxygen consumption and superoxide release as indices of the overall state of oxygen metabolism of these cells reflecting the integrity of PAM oxidative mechanisms of microbicidal activity, and chemotaxis, an event clinically important for normal defense to infection. In vitro incubation with cyclosporine at concentrations as low as 10(-9) M caused a 52% inhibition of PAM superoxide release, but Az had no effect at concentrations up to 10(-6) M. Prednisolone caused a 38% inhibition of superoxide release; comparable levels of inhibition with Pr required concentrations at least 10-fold greater than with cyclosporine. Further experiments indicated that cyclosporine induced a 40% inhibition after contact with PAM for only 30 min. In vivo experiments indicated that cyclosporine (5 mg/kg), Az (20 mg/kg), or Pr (2 or 0.5 mg/kg) administered intraperitoneally had no effect on the number of PAM available for host defense, PAM oxygen consumption, or PAM superoxide release. However, PAM from cyclosporine-treated animals demonstrated complete inhibition of active migration or chemotaxis in modified Boyden chambers upon incubation with formylmethionyl-leucyl-phenylalanine (FMLP). The effect was apparently dampened by simultaneous administration of Pr with cyclosporine. These experiments suggest that with the exception of a marked effect on chemotaxis the in vivo effects of physiologic amounts of cyclosporine on PAM function are modest compared with the marked depression after in vitro addition.

Murine cellular cytotoxicity to syngeneic and xenogeneic herpes simplex virus-infected cells.

Cellular cytotoxicity of C57BL/6 adult mice peritoneal cells to xenogeneic (Chang liver) and syngeneic (BL/6-WT3) herpes simplex virus (HSV)-infected cells was analyzed in a 6-h 51Cr release assay. There was no difference in antibody-dependent cellular cytotoxicity to either target. There was no natural killer cytotoxicity to targets with cells from uninfected mice except at very high effector cell ratios. HSV-infected (2 X 10(4) PFU intraperitoneally 1 day previously) mice mediated significantly higher antibody-dependent cellular cytotoxicity and required less antibody (10(-5) versus 10(-2) dilution), fewer cells, and less time to kill than cells from uninfected mice. HSV-infected mice mediated natural killer cytotoxicity but preferentially killed syngeneic HSV-infected cells. Stimulation of cytotoxicity was not virus specific since influenza-infected mice mediated similar levels of cytotoxicity to HSV-infected targets. There was no difference in morphology (95% macrophage) or in the percentage of FcR-positive cells, but infected mice had more peritoneal cells and generated higher levels of superoxide in response to opsonized zymosan or phorbolmyristate acetate. These data demonstrate nonspecific virus-stimulated metabolic and effector cell function which may enhance clearance of virus in an infected host.

The effects of clofibrate ingestion on alveolar macrophage peroxisome content and oxygen metabolism.

Respiratory burst activity in alveolar macrophages in response to particulate and soluble challenges, such as zymosan particles and phorbol myristate acetate (PMA), is not nearly as dependent upon membrane stimulation as in neutrophils. Microperoxisomes are subcellular organelles containing catalase and are present in lung macrophages and cells of other organs. Evidence from liver cells indicates that peroxisomes are intimately involved with hydrogen peroxide and lipid metabolism. Clofibrate (2-(p-chlorophenoxy)-2-methylpropionic acid ethyl, Atromid-S-), a hypolipidemic drug known to cause peroxisomal proliferation in liver cells, was studied with respect to its ability to cause increases in the microperoxisome content and to alter the cellular metabolism of alveolar macrophages. Liver weight increased over a 2-week drug treatment period while lung weight remained unchanged. Plasma triglyceride levels were decreased by the treatment, indicating the effectiveness of the drug. Unlike the effect on liver cells, however, clofibrate did not cause a proliferation of microperoxisomes, as determined by morphometric analysis. Oxygen consumption and hydrogen peroxide generation by alveolar macrophages in response to either stimulant (zymosan or PMA) was no greater in clofibrate-treated rats than in controls. Superoxide release, when expressed as the change in response to PMA, appeared elevated in the drug group; statistical significance, however, was not demonstrated. The hexose monophosphate shunt (HMP), which produces reducing equivalents for lipid biosynthesis, was elevated in macrophages from clofibrate-treated rats when expressed similarly. The significance of these results in relation to the known effects of the drug on liver cells.

Characterization of a postlavage, in situ pulmonary macrophage population.

A postlavage in situ subpopulation of pulmonary macrophages (PM), biochemically distinct from the lavaged population, has recently been isolated from rats. After exhaustive bronchopulmonary lavage to extract the free lung cells, the lungs were excised, homogenized, and filtered, and the resultant cell suspension was allowed to form a monolayer on plastic Petri dishes. Electron microscopic morphometry failed to indicate any morphologic differences in the two populations. The postlavage in situ PM were more active metabolically during phagocytosis of zymosan particles or stimulation by phorbol myristate acetate (PMA) than the corresponding lavage population, as evidenced by greater superoxide generation. Macrophages prepared by either method became more avidly phagocytic when incubated with cell-free medium isolated in the preparation of the situ population. Peroxidase, an enzyme absent from the granules of PM separated by lavage techniques, was found in a granule-rich fraction of the in situ macrophage. Catalase activity was found in similar amounts in both supernatants and granule-rich fractions of both populations. The results support the concept of subpopulations of PM and suggest that these subpopulations are distinguished by their biochemical properties and their functional abilities.

Functional and metabolic properties of alveolar macrophages in response to the gas phase of tobacco smoke.

The effect of whole tobacco smoke and the gas phase of tobacco smoke on the metabolism and phagocytic ability of alveolar macrophages was monitored over a 30-day exposure period. It was demonstrated that both the gas phase and whole tobacco smoke induced a weight loss in exposed rats. Alveolar macrophage oxygen consumption was markedly increased by both exposure regimens. Superoxide generation was not affected by whole tobacco smoke exposure but was increased in response to the filtered gas phase. Hexose monophosphate shunt activity was not altered by either treatment. When metabolic alterations were seen in response to the separate exposures, they were seen only after a phagocytic challenge to the macrophage and not when the cell was unchallenged. Neither whole tobacco smoke nor the gas phase had any significant effect on the ability of alveolar macrophages to phagocytize a viable challenge of Staphylococcus aureus. Our results suggest that many of the metabolic and functional effects of tobacco smoke on alveolar macrophages can be attributed to the gas-phase component of whole tobacco smoke.