Macrophage Bactericidal Function Research Articles

EGFR-MEK1/2 cascade negatively regulates bactericidal function of bone marrow macrophages in mice with Staphylococcus aureus osteomyelitis.

The ability of Staphylococcus aureus (S. aureus) to survive within macrophages is a critical strategy for immune evasion, contributing to the pathogenesis and progression of osteomyelitis. However, the underlying mechanisms remain poorly characterized. This study discovered that inhibiting the MEK1/2 pathway reduced bacterial load and mitigated bone destruction in a mouse model of S. aureus osteomyelitis. Histological staining revealed increased phosphorylated MEK1/2 levels in bone marrow macrophages surrounding abscess in the mouse model of S. aureus osteomyelitis. Activation of MEK1/2 pathway and its roles in impairing macrophage bactericidal function were confirmed in primary mouse bone marrow-derived macrophages (BMDMs). Transcriptome analysis and in vitro experiments demonstrated that S. aureus activates the MEK1/2 pathway through EGFR signaling. Moreover, we found that excessive activation of EGFR-MEK1/2 cascade downregulates mitochondrial reactive oxygen species (mtROS) levels by suppressing Chek2 expression, thereby impairing macrophage bactericidal function. Furthermore, pharmacological inhibition of EGFR signaling prevented upregulation of phosphorylated MEK1/2 and restored Chek2 expression in macrophages, significantly enhancing S. aureus clearance and improving bone microstructure in vivo. These findings highlight the critical role of the EGFR-MEK1/2 cascade in host immune defense against S. aureus, suggesting that S. aureus may reduce mtROS levels by overactivating the EGFR-MEK1/2 cascade, thereby suppressing macrophage bactericidal function. Therefore, combining EGFR-MEK1/2 pathway blockade with antibiotics could represent an effective therapeutic approach for the treatment of S. aureus osteomyelitis.

Mycobacterium tuberculosis reduces global histone acetylation in human macrophages which is restored by Sirtuin inhibitors

Abstract Mycobacterium tuberculosis (Mtb) infects and grows in human macrophages unless they are activated earlier using IFN-γ. IFN-γ polarized M1-Macrophages (MΦs) and IL-4 driven M2-MΦs respectively kill Mtb or are permissive. Mtb infected M1-MΦs showed an increased expression of iNOS and autophagy-regulating ATGs compared to M2-MΦs. Despite increased bactericidal function, M1-MΦs were unable to eradicate Mtb. Hypothesis Because M1- and M2-MΦs differentially expressed Sirtuin1, 2, 3 and Sirt5, we hypothesized that, Sirtuin-dependent histone deacetylation would affect gene expression and bactericidal function Methods M0 (naive), M1 or M2-MΦs were treated with inhibitors of Sirtuin1, Sirt2, Sirt3 and Sirt5 followed by Mtb infection, and evaluation of histone modifications using a novel triomics approach. Viability of Mtb was measured before and after Sirtuin blockade and correlated to mRNA expression for iNOS and ATG5 using qPCR. Results a) Relative to uninfected M0-MΦs, M1-MΦs showed higher levels of histone acetylation followed by M2-MΦs. b) Mtb infection reduced global histone acetylation in all three MΦ phenotypes, with an concurrent increase in histone methylation. c) Blockade of Sirt1, 2, 3 but not Sirt5 led to a dramatic restoration of histone acetylation in all three phenotypes, although M2-MΦs were still resistant to Sirt3 inhibitors. d) M0, M1- and M2-MΦs killed Mtb more effectively after Sirt2 blockade compared to Sirt1, 3 and 5 inhibition, which was associated with an increase in mRNA for iNOS and ATG5. Conclusion We conclude that Mtb decreases histone acetylome of human MΦs and Sirtuin inhibitors provide a new epigenetic mechanism to restore macrophage bactericidal function against tuberculosis. Supported by NIH NIAID RO1 AI-122070 and AI-161015.

The Clinical Value of GDF15 and Its Prospective Mechanism in Sepsis.

Growth differentiation factor 15 (GDF15) is involved in the occurrence and development of many diseases, and there are few studies on its relationship with sepsis. This article aims to explore the clinical value of GDF15 in sepsis and to preliminarily explore its prospective regulatory effect on macrophage inflammation and its functions. We recruited 320 subjects (132 cases in sepsis group, 93 cases in nonsepsis group, and 95 cases in control group), then detected the serum GDF15 levels and laboratory indicators, and further investigated the correlation between GDF15 and laboratory indicators, and also analyzed the clinical value of GDF15 in sepsis diagnosis, severity assessment, and prognosis. In vitro, we used LPS to stimulate THP-1 and RAW264.7 cells to establish the inflammatory model, and detected the expression of GDF15 in the culture medium and cells under the inflammatory state. After that, we added GDF15 recombinant protein (rGDF15) pretreatment to explore its prospective regulatory effect on macrophage inflammation and its functions. The results showed that the serum GDF15 levels were significantly increased in the sepsis group, which was correlated with laboratory indexes of organ damage, coagulation indexes, inflammatory factors, and SOFA score. GDF15 also has a high AUC in the diagnosis of sepsis, which can be further improved by combining with other indicators. The dynamic monitoring of GDF15 levels can play an important role in the judgment and prognosis of sepsis. In the inflammatory state, the expression of intracellular and extracellular GDF15 increased. GDF15 can reduce the levels of cytokines, inhibit M1 polarization induced by LPS, and promote M2 polarization. Moreover, GDF15 also enhances the phagocytosis and bactericidal function of macrophages. Finally, we observed a decreased level of the phosphorylation of JAK1/STAT3 signaling pathway and the nuclear translocation of NF-κB p65 with the pretreatment of rGDF15. In summary, our study found that GDF15 has good clinical application value in sepsis and plays a protective role in the development of sepsis by regulating the functions of macrophages and inhibiting the activation of JAK1/STAT3 pathway and nuclear translocation of NF-κB p65.

Two-phase releasing immune-stimulating composite orchestrates protection against microbial infections

Sepsis, a syndrome of acute organ dysfunction induced by various infections, could lead to a very high mortality in hospitals despite the development of advanced medical technologies. Herein, a type of two-phase releasing immune-stimulating composite is developed by mixing alginate (ALG) with muramyl dipeptide (MDP) and the nanoparticle formulation of monophosphoryl lipid A (MPLA), the latter two are immunomodulatory agents with different release rates from the formed ALG hydrogel. The obtained two phase-releasing composite could provide instantaneous sepsis protection by the rapid release of MDP to enhance the phagocytic and bactericidal function of macrophages. Later on, such composite could further offer long-term sepsis protection by the sustained release of MPLA to continuously activate the immune system, via up-regulating the production of various pro-inflammatory cytokines, promoting the polarization of macrophages, and increasing the percent of natural killer (NK) cells in the lesion after sepsis challenge. Mice survived from sepsis challenge after such treatment could resist a second infection. Notably, treatment with our composite could increase the mouse survival rate in a cecal ligation and puncture (CLP) induced polymicrobial sepsis model. This work provides an easy-translatable immune-stimulating formulation for effective protection against sepsis under various triggering causes. Our strategy may be promising for long-term broad prevention against various infections, and could potentially be used to protect medical workers under a new pandemic before a reliable vaccine is available.

Saposin D acting on macrophage bacteriostatic function in experimental tuberculosis infection

The protection against tuberculosis infection is largely determined by the ability of host tissue macrophages to limit the growth and spread of mycobacteria. Able to multiply within the host macrophages, mycobacteria have developed a number of protective mechanisms preventing phagosome-lysosome fusion, thereby evading damaging effects of lysosomal enzymes. Saposins are small, acidic, thermostable, non-enzymatic glycoproteins that participate as co-fac-tors in degradation of short oligosaccharide head group glycosphingolipids. Saposins A, B, C and D are formed in acidic endosomes due to cleavage of initial prosaposin molecule. The effect of saposins on human immune response is mediated by their involvement in presenting mycobacterial antigens on CD1 molecules. Preliminary studies with electron microscopy allowed to uncover saposin D-bound damaging effect on Mycobacterium tuberculosis in acidic environment. These data allowed us to suggest that saposin D is an important protective component fighting against TB infection. The aim of the study was to explore how saposin D deficiency might affect formation of anti-tuberculosis immune response and ability of macrophages to inhibit M. tuberculosis growth. Materials and methods. Interstitial pulmonary macrophages and peritoneal macrophages were isolated from wild type C57BL/6 strain and saposin D deficient C57BL/6-SapD-/- mouse strains. Results. It was found that as compared to macrophages from mice, macrophages from wild type strain significantly better controlled mycobacteria growth in vitro. To study an opportunity of compensating for deficient saposin D in peritoneal macrophages from C57BL/6-SapD-/- mice, a saposin D gene-bearing lentiviral vector was created. Transfection of SAPD-deficient peritoneal macrophages with expression vector compensated for saposin D deficiency in such cells and restored bactericidal function. The mechanisms of action for current anti-TB drugs are mediated by various metabolic pathways in mycobacteria (inhibited biosynthesis of fatty acids, arabinogalactan, peptidoglycan and protein; inhibition of DNA-dependent processes, proton pumps and cytochrome P450-dependent monooxygenases). Conclusion. It was shown that saposin D deficiency affects activation of macrophage bactericidal function in vitro. Our study data may be a prerequisite for biologically substantiated potential of using a vector construct bearing natural human protein gene such as saposin D, as a new anti-tuberculosis drug.

S1PR3 Signaling Drives Bacterial Killing and Is Required for Survival in Bacterial Sepsis.

Efficient elimination of pathogenic bacteria is a critical determinant in the outcome of sepsis. Sphingosine-1-phosphate receptor 3 (S1PR3) mediates multiple aspects of the inflammatory response during sepsis, but whether S1PR3 signaling is necessary for eliminating the invading pathogens remains unknown. To investigate the role of S1PR3 in antibacterial immunity during sepsis. Loss- and gain-of-function experiments were performed using cell and murine models. S1PR3 levels were determined in patients with sepsis and healthy volunteers. S1PR3 protein levels were up-regulated in macrophages upon bacterial stimulation. S1pr3-/- mice showed increased mortality and increased bacterial burden in multiple models of sepsis. The transfer of wild-type bone marrow-derived macrophages rescued S1pr3-/- mice from lethal sepsis. S1PR3-overexpressing macrophages further ameliorated the mortality rate of sepsis. Loss of S1PR3 led to markedly decreased bacterial killing in macrophages. Enhancing endogenous S1PR3 activity using a peptide agonist potentiated the macrophage bactericidal function and improved survival rates in multiple models of sepsis. Mechanically, the reactive oxygen species levels were decreased and phagosome maturation was delayed in S1pr3-/- macrophages due to impaired recruitment of vacuolar protein-sorting 34 to the phagosomes. In addition, S1RP3 expression levels were elevated in monocytes from patients with sepsis. Higher levels of monocytic S1PR3 were associated with efficient intracellular bactericidal activity, better immune status, and preferable outcomes. S1PR3 signaling drives bacterial killing and is essential for survival in bacterial sepsis. Interventions targeting S1PR3 signaling could have translational implications for manipulating the innate immune response to combat pathogens.

Glucocorticoid-Augmented Efferocytosis Inhibits Pulmonary Pneumococcal Clearance in Mice by Reducing Alveolar Macrophage Bactericidal Function.

Inhaled corticosteroids (ICS) increase community-acquired pneumonia (CAP) incidence in patients with chronic obstructive pulmonary disease (COPD) by unknown mechanisms. Apoptosis is increased in the lungs of COPD patients. Uptake of apoptotic cells (ACs) ("efferocytosis") by alveolar macrophages (AMøs) reduces their ability to combat microbes, including Streptococcus pneumoniae, the most common cause of CAP in COPD patients. Having shown that ICS significantly increase AMø efferocytosis, we hypothesized that this process, termed glucocorticoid-augmented efferocytosis, might explain the association of CAP with ICS therapy in COPD. To test this hypothesis, we studied the effects of fluticasone, AC, or both on AMøs of C57BL/6 mice in vitro and in an established model of pneumococcal pneumonia. Fluticasone plus AC significantly reduced TLR4-stimulated AMø IL-12 production, relative to either treatment alone, and decreased TNF-α, CCL3, CCL5, and keratinocyte-derived chemoattractant/CXCL1, relative to AC. Mice treated with fluticasone plus AC before infection with viable pneumococci developed significantly more lung CFUs at 48 h. However, none of the pretreatments altered inflammatory cell recruitment to the lungs at 48 h postinfection, and fluticasone plus AC less markedly reduced in vitro mediator production to heat-killed pneumococci. Fluticasone plus AC significantly reduced in vitro AMø killing of pneumococci, relative to other conditions, in part by delaying phagolysosome acidification without affecting production of reactive oxygen or nitrogen species. These results support glucocorticoid-augmented efferocytosis as a potential explanation for the epidemiological association of ICS therapy of COPD patients with increased risk for CAP, and establish murine experimental models to dissect underlying molecular mechanisms.

E3 ubiquitin ligase NKLAM positively regulates nitric oxide production and the generation of reactive oxygen species in macrophages (P4167)

Abstract Stimulated macrophages generate potent anti-microbial reactive oxygen and nitrogen species within their phagosomes. There is mounting evidence that ubiquitination plays a role in modulating macrophage bactericidal functions. Recently, we demonstrated that the ubiquitin ligase NKLAM was a component of the macrophage phagosome. In this present study we investigated the effects of NKLAM on macrophage generation of nitric oxide (NO) and reactive oxygen species. Stimulation with LPS induced wild type (WT) macrophages to produce NO in a time and concentration-dependent manner. NO production was attenuated in NKLAM-knock out (KO) macrophages. We also found that inducible nitric oxide synthase (iNOS) protein expression was lower and that iNOS translocation to the maturing phagosome was defective in KO macrophages. In vivo, intraperitoneal injection of LPS induced a time-dependent increase in serum nitrite (NO metabolite) in both WT and KO mice. However, nitrite levels in KO mice were lower than in WT mice. The generation of reactive oxygen species (ROS) is a potent killing mechanism; however the role of ubiquitination in regulating ROS generation is unclear. To this end, we investigated ROS production in WT and KO macrophages and found that ROS production was defective in KO macrophages stimulated with either PMA or Escherichia coli. Collectively, our data implicate NKLAM as a potent modulator of macrophage oxidative killing functions.

E3 ubiquitin ligase NKLAM is a macrophage phagosome protein and plays a role in bacterial killing

Macrophages are a critically important component of the innate and adaptive immune systems. They are equipped with oxidative and non-oxidative mechanisms to kill ingested pathogens. Natural Killer Lytic-Associated Molecule (NKLAM) is an E3 ubiquitin ligase expressed in macrophages and natural killer cells. We show that NKLAM expression in macrophages was enhanced by Toll-like receptor agonists and pro-inflammatory cytokines. Using confocal microscopy, we found that NKLAM colocalized with ingested Escherichia coli. In assays using IgG-opsonized latex beads as targets, we demonstrated that NKLAM translocated to the phagosome early during maturation at a time that coincided with elevated levels of ubiquitinated phagosome proteins. In killing assays with bone marrow-derived macrophages from wild type and NKLAM-deficient mice, we found that NKLAM-deficient macrophages demonstrated less killing of E. coli than wild type macrophages. Collectively, our data show that NKLAM is a novel component of macrophage phagosomes and is involved in macrophage bactericidal functions.

Natural killer lytic-associated molecule is a component of macrophage phagosomes and contributes to bacterial killing (117.23)

Abstract Macrophages are a critically important component of the immune system. They are equipped with oxidative and non-oxidative mechanisms to kill pathogens that have been compartmentalized into phagosomes following phagocytosis. Ubiquitin, a small protein modifier that regulates protein degradation, has been found to play a role in macrophage bacterial killing. Natural killer lytic-associated molecule (NKLAM) is an E3 ubiquitin ligase expressed in macrophages and natural killer cells. We have shown that NKLAM expression in macrophages is enhanced by Toll-like receptor agonists and pro-inflammatory cytokines. Using bone marrow-derived macrophages from wild type (WT) and NKLAM-deficient mice we found the levels of phagocytosis and phagosome acidification to be similar; however, killing of E. coli by NKLAM-deficient macrophages is less than by WT macrophages. Using confocal immunofluorescence microscopy, we found that NKLAM is colocalized with ingested bacteria. In assays using IgG-opsonized latex beads as targets, we demonstrated that NKLAM is translocated to the phagosome early in the maturation process. In addition, the presence of NKLAM in the phagosome temporally coincides with increased levels of ubiquitin. Collectively, our data demonstrate that NKLAM is a novel component of macrophage phagosomes and that NKLAM is involved in macrophage bactericidal functions.

A Cardinal Role for Cathepsin D in Co-Ordinating the Host-Mediated Apoptosis of Macrophages and Killing of Pneumococci

The bactericidal function of macrophages against pneumococci is enhanced by their apoptotic demise, which is controlled by the anti-apoptotic protein Mcl-1. Here, we show that lysosomal membrane permeabilization (LMP) and cytosolic translocation of activated cathepsin D occur prior to activation of a mitochondrial pathway of macrophage apoptosis. Pharmacological inhibition or knockout of cathepsin D during pneumococcal infection blocked macrophage apoptosis. As a result of cathepsin D activation, Mcl-1 interacted with its ubiquitin ligase Mule and expression declined. Inhibition of cathepsin D had no effect on early bacterial killing but inhibited the late phase of apoptosis-associated killing of pneumococci in vitro. Mice bearing a cathepsin D−/− hematopoietic system demonstrated reduced macrophage apoptosis in vivo, with decreased clearance of pneumococci and enhanced recruitment of neutrophils to control pulmonary infection. These findings establish an unexpected role for a cathepsin D-mediated lysosomal pathway of apoptosis in pulmonary host defense and underscore the importance of apoptosis-associated microbial killing to macrophage function.

Development of new antituberculous drugs based on bacterial virulence factors interfering with host cytokine networks

The worldwide increase in the prevalence of tuberculosis (TB), especially multidrug-resistant TB and extensively drug-resistant TB, is an important global health concern, and new effective drugs are urgently needed. Information on the genome of Mycobacterium tuberculosis (MTB) and various mycobacterial virulence genes is leading to the identification of genes that code for new drug targets. Mycobacterium tuberculosis (MTB) is resistant to the antimicrobial mechanisms of host macrophages and can survive and replicate in macrophages for long periods, resulting in a persistent infection. Mycobacterial virulence factors suppress macrophage bactericidal functions partly via their downregulatory effects on the host antimicrobial cytokine networks, consisting of proinflammatory, immunopotentiating, and Th1-inducing cytokines. Thus, for the development of unique drugs that exhibit antimycobacterial action through novel mechanisms, it is reasonable to search for targets among bacterial genes encoding virulence factors which interfere with the host cytokine responses protective to mycobacterial pathogens. In this review, we discuss the profiles of cytokine networks related to host resistance to mycobacteria, including the mechanisms of downregulation of host antimycobacterial immunity due to immunosuppressive cytokines, which are occasionally induced in the advanced stages of TB. We also highlight the development of antituberculous drugs based on bacterial virulence factors interfering with the host antimycobacterial cytokine network.

Human monocytes and monocyte-derived macrophage phagocytosis of serotype III group B streptococci strains.

In this report group B streptococci (GBS) strains 90356 and 80340 isolated from liquor and vagina, respectively, were placed into contact with human peripheral blood monocytes (PBM) and macrophages derived from monocytes (MDM) by differentiation in vitro. The increased expression of CD16 and CD68 by macrophages cultured for 7 days compared with adherent monocytes supported the distinct maturation status of these cells. The number of viable intracellular bacteria of the 90356 strain was observed after 2 h of incubation with PBM (P < 0.001) and 0.5 h with MDM (P < 0.001). MDM cells seemed to present a more efficient mechanism of bacterial destruction of GBS type III, isolated from a case of meningitis. Viable cells of strain 80340, isolated from the vagina, were not detected in significant numbers in PBM and MDM phagocytic cells. These findings add to our current understanding of the roles played by multiple receptor-ligand systems in the uptake and pathogenesis of group B streptococci infection. Survival strategies of GBS, which interfere with macrophage bactericidal functions, might exist.

Effect of short-term enteral feeding with eicosapentaenoic and gamma-linolenic acids on alveolar macrophage eicosanoid synthesis and bactericidal function in rats.

Because vasoactive eicosanoids derived from arachidonic acid present in immune cell phospholipids promote lung inflammation in critically ill patients, novel experimental diets containing eicosapentaenoic acid from fish oil and gamma-linolenic acid from borage oil have been designed to limit arachidonic acid metabolism. However, excess dietary eicosapentaenoic acid impairs superoxide formation and bacterial killing by immune cells. The present study determined whether short-term enteral feeding with diets enriched with either eicosapentaenoic acid alone or in combination with gamma-linolenic acid would modulate alveolar macrophage eicosanoid synthesis without compromising bactericidal function. Prospective, randomized, controlled, blinded study. University medical center. Adult male Sprague-Dawley rats. Rats underwent surgical placement of a gastroduodenal feeding catheter and were randomly assigned to receive one of three high-fat (55.2% of total calories), low-carbohydrate diets containing isocaloric amounts of lipids for 4 days. The control diet was enriched with linoleic acid, whereas the two test diets were low in linoleic acid and enriched with either 5 mole % eicosapentaenoic acid alone or in combination with 5 mole % gamma-linolenic acid. Alveolar macrophages were then procured to assess phospholipid fatty acid composition, eicosanoid synthesis after stimulation with endotoxin, superoxide formation and phagocytosis by flow cytometry, and killing of Staphylococcus aureus Alveolar macrophage levels of arachidonic acid were significantly (p < .01) lower and levels of eicosapentaenoic and dihomo-gamma-linolenic acids were higher after feeding the eicosapentaenoic and gamma-linolenic acid diet vs. the linoleic acid diet. Ratios of thromboxane B2,/B3, leukotriene B4/B5, and prostaglandin E2/E1 were reduced in the macrophages from rats given either the eicosapentaenoic acid or eicosapentaenoic acid with gamma-linolenic acid diet compared with ratios from rats given the linoleic acid diet. Macrophages from rats given the eicosapentaenoic with gamma-linolenic acid diet released 35% or 24% more prostaglandin E1 than macrophages from rats given either the linoleic acid or the eicosapentaenoic acid diet, respectively. Macrophage superoxide generation, phagocytosis of opsonized zymosan, and killing of S. aureus were similar irrespective of dietary treatment. Short-term enteral feeding with an eicosapentaenoic acid-enriched or eicosapentaenoic with gamma-linolenic acid-enriched diet rapidly modulated the fatty acid composition of alveolar macrophage phospholipids, promoted a shift toward formation of less inflammatory eicosanoids by stimulated macrophages, but did not impair alveolar macrophage bactericidal function relative to responses observed after feeding a linoleic acid diet.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) enhances pulmonary defenses against pneumococcal infections after splenectomy.

Splenectomized individuals are at risk for pneumococcal sepsis. Alveolar macrophage bactericidal function is depressed after splenectomy. Granulocyte-macrophage colony-stimulating factor (GM-CSF) has pronounced effects on the number and function of macrophages. We hypothesized that GM-CSF treatment could improve alveolar macrophage bactericidal activity against pneumococci, and improve survival with pneumococcal infection. Two weeks after splenectomy or sham operation, mice were treated with GM-CSF or saline twice daily for varying times. Alveolar macrophages were obtained by bronchopulmonary lavage, and bactericidal activity was measured. Survival was assessed after pneumococcal aerosol challenge. Alveolar macrophage bactericidal activity was improved with GM-CSF treatment in both eusplenic and asplenic mice (p < 0.001). GM-CSF treatment improved survival in both groups (p < 0.001). GM-CSF can augment alveolar macrophage function and provide protection against pneumococcal infections. It may be a useful adjuvant therapy for normal and splenectomized individuals.

Augmentation of alveolar macrophage phagocytic activity by granulocyte colony stimulating factor and interleukin-1: influence of splenectomy.

The use of cytokines and other naturally occurring substances as biopharmaceuticals for modulating the host response to trauma and infection offers new therapeutic possibilities. Cytokine pretreatment protects animals in a variety of experimental models, including splenectomized mice following pneumococcal aerosol challenge. Since splenectomy appears to affect alveolar macrophage function, we postulated that pretreatment with interleukin 1 (IL-1) and granulocyte colony stimulating factor (G-CSF) improved survival in mice following aerosol challenge of live pneumococci by activating alveolar macrophages. Alveolar macrophage bactericidal and phagocytic function was slightly, but consistently, depressed following splenectomy. Interleukin-1 and G-CSF pretreatment had pronounced effects on macrophage phagocytic and bactericidal activity, and these effects were quite different depending upon whether the mice were eusplenic or asplenic. Splenectomy augmented the effects of IL-1 on alveolar macrophage bactericidal function compared with eusplenic mice (p < 0.001), while more pronounced effects on macrophage function following G-CSF treatment were seen in mice with intact spleens (p < 0.001). The use of cytokines and other substances to modify the host response to infection has great potential. Individuals with deficits such as splenectomy will have a different net response to therapy. It is important that we be able to predict these responses accurately in most patients in order to use these substances more effectively.

Genetic control of resistance to Mycoplasma pulmonis infection in mice

The differences in susceptibility of various inbred strains of mice to a highly pathogenic strain of Mycoplasma pulmonis CT (T2) has been known for some time. We assessed the genetic control of resistance to T2 infection. Tracheolung lavage samples and lungs of mice were assessed for T2 organisms after intratracheal injection of T2. We found that H-2b (C57BL/6 (B6) and H-2k B10.BR mice were resistant, whereas H-2b A.By, H-2k C3H/Bi, H-2k C3H/HeJ (C3H), and H-2b BALB.B mice were susceptible. We also typed individual B6C3F2 mice for H-2 and for resistance to T2 and observed that resistance to T2 infections is controlled by a single dominant gene not linked to H-2. Histologic examination revealed severe lung lesions typical of M. pulmonis infections in susceptible C3H mice, in contrast to minimal lung lesions in resistant B6 mice. No significant titers of local or systemic antimycoplasma antibodies were detected in either resistant or susceptible mice at 5 days postinfection. Macrophages taken from uninfected B6 or C3H mice failed to inhibit growth of T2 in vitro. However, macrophages from B6 mice did inhibit growth of T2 much better than C3H macrophages when harvested on day 5 of infection. Thus, there is an association between activation of macrophage bactericidal function and genetic resistance to growth of T2 organisms.

Malacoplasie: À propos d'une observation avec localisation rétropéritonéale

Malacoplakia is a granulomatous inflammatory disease caused by a disorder of macrophage bactericidal function. The disease, histologically characterized by the presence of Michaelis-Gutmann bodies, has a preference for the urogenital tract and less frequently affects the gastrointestinal tract and the retroperitoneal region. We report the unusual case of a male patient who presented with retroperitoneal pseudotumoral malacoplakia associated with vesical malacoplakia. The main pathophysiological, diagnostic and therapeutic aspects of this rare disease are described.

Corynebacterium parvum can Reverse the Depression of Macrophage Hydrogen Peroxide Production Caused by Erythrocyte Phagocytosis

Our previous studies have shown that the phagocytosis of IgG-coated erythrocytes (EIgG) in vivo increases the mortality rate with bacterial infection, and EIgG phagocytosis in vitro depresses phorbol myristate acetate (PMA)-triggered H2O2 production. The present study was undertaken to determine if the depression of H2O2 production caused by EIgG phagocytosis could be reversed by exposing macrophages to priming agents. Macrophages exposed to 100 micrograms/ml of C. parvum, it's pyridine-soluble extract (PE), or the pyridine extract residue (PER) for 1 hr showed an enhanced production of H2O2 in response to PMA triggering. The priming effect of C. parvum, PE, and PER lasted for 3-6 hr. 18 hr after exposure to C parvum or PER, PMA-triggered H2O2 production was depressed, however PE did not have this effect. The priming effect of C parvum was not prevented by cycloheximide. EIgG phagocytosis caused a dose dependent depression of PMA-triggered H2O2 production. When macrophages were exposed to C. parvum, PE, or PER following EIgG phagocytosis, the priming of PMA-triggered H2O2 production was reduced but H2O2 production was maintained at levels equal to or greater than that of control macrophages. These results show that phagocytosis did not prevent the action of priming agents on macrophage respiratory burst capacity, and suggests that such agents may preserve macrophage bactericidal function following phagocytosis.

Effects of anti-inflammatory Agent No.6 for injection on the oxidative burst of rat peritoneal macrophages.

Anti-inflammatory Agent No.6 for injection (AI-6) is an effective anti-infective agent composed of four traditional Chinese medicinal herbs. It was demonstrated in our experiment that the agent was able to enhance oxidative burst of rat peritoneal macrophages as shown by the increased production of H2O2 and increased reduction of nitroblue tetrazolium (NBT). It seems likely that by these means AI-6 could promote the bactericidal function of macrophages. NBT reduction of macrophages was observed by both spectrophotometric quantification and electron microscopy.