Production of granulocyte-macrophage colony-stimulating factor (GM-CSF) by monocytes and large granular lymphocytes stimulated with Mycobacterium avium-M. intracellulare: activation of bactericidal activity by GM-CSF

HDL and plaque regression in a multiphase model of early atherosclerosis

Atherosclerosis is a chronic disease of the arteries characterised by the accumulation of lipids and lipid-engorged cells in the artery wall. Early plaque growth is aggravated by the deposition of low density lipoproteins (LDL) in the wall and the subsequent immune response. High density lipoproteins (HDL) counterbalance the effects of LDL by accepting cholesterol from macrophages and removing it from the plaque. In this paper, we develop a free boundary multiphase model to investigate the effects of LDL and HDL on early plaque development. We examine how the rates of LDL and HDL deposition affect cholesterol accumulation in macrophages, and how this impacts cell death rates and emigration. We identify a region of LDL-HDL parameter space where plaque growth stabilises for low LDL and high HDL influxes, due to macrophage emigration and HDL clearance that counterbalances the influx of new cells and cholesterol. We explore how the efferocytic uptake of dead cells and the recruitment of new macrophages affect plaque development for a range of LDL and HDL influxes. Finally, we consider how changes in the LDL-HDL profile can change the course of plaque development. We show that changes towards lower LDL and higher HDL can slow plaque growth and even induce regression. We find that these changes have less effect on larger, more established plaques, and that temporary changes will only slow plaque growth in the short term.

Macrophage Anti-inflammatory Behaviour in a Multiphase Model of Atherosclerotic Plaque Development

Atherosclerosis is an inflammatory disease characterised by the formation of plaques, which are deposits of lipids and cholesterol-laden macrophages that form in the artery wall. The inflammation is often non-resolving, due in large part to changes in normal macrophage anti-inflammatory behaviour that are induced by the toxic plaque microenvironment. These changes include higher death rates, defective efferocytic uptake of dead cells, and reduced rates of emigration. We develop a free boundary multiphase model for early atherosclerotic plaques, and we use it to investigate the effects of impaired macrophage anti-inflammatory behaviour on plaque structure and growth. We find that high rates of cell death relative to efferocytic uptake results in a plaque populated mostly by dead cells. We also find that emigration can potentially slow or halt plaque growth by allowing material to exit the plaque, but this is contingent on the availability of live macrophage foam cells in the deep plaque. Finally, we introduce an additional bead species to model macrophage tagging via microspheres, and we use the extended model to explore how high rates of cell death and low rates of efferocytosis and emigration prevent the clearance of macrophages from the plaque.

Patients with Idiopathic Pulmonary Nontuberculous Mycobacterial Disease Have Normal Th1/Th2 Cytokine Responses but Diminished Th17 Cytokine and Enhanced Granulocyte-Macrophage Colony-Stimulating Factor Production

Objective

Although disseminated nontuberculous mycobacterial infection is attributed to defects in the interleukin (IL)-12/interferon-γ circuit, the immunophenotype of idiopathic pulmonary nontuberculous mycobacterial (PNTM) disease is not well defined.

Method

We phenotyped Th1, Th2, Th17, and Treg cytokines and colony-stimulating factor production from patients with idiopathic PNTM disease. Data were compared with healthy donors, cystic fibrosis (CF), and primary ciliary dyskinesia (PCD) patients with PNTM disease. Both supernatant cytokine production and intracellular cytokines expressed by various leukocyte subpopulations following mitogen and antigen stimulation were assayed by electrochemiluminescence-based multiplex immunoassay and flow cytometry, respectively.

Results

Regardless of antigen or mitogen stimulation, neither intracellular nor extracellular Th1, Th2, and Treg cytokine levels differed between patients and controls. Th17 cells and IL-17A levels were lower in idiopathic PNTM patients, whereas monocyte granulocyte-macrophage colony-stimulating factor (GM-CSF) expression in response to NTM stimulation was higher compared with healthy donors. Besides, distinct cytokine responses following stimulation by Mycobacterium abscessus and Mycobacterium avium were observed consistently within each group.

Conclusions

The IL-12/IFN-γ circuit appeared intact in patients with idiopathic PNTM disease. However, idiopathic PNTM patients had reduced Th17 response and higher mycobacteria-induced monocyte GM-CSF expression.

Johne's disease in cattle: an in vitro model to study early response to infection of Mycobacterium avium subsp. paratuberculosis using RNA-seq

Johne's disease is a chronic granulomatous enteritis caused by Mycobacterium avium subsp. paratubercolosis (MAP) which affects ruminants worldwide and has a significant economic impact. MAP has also been associated with human Crohn's disease, although this connection is not well established. MAP is highly adapted for survival within host macrophages and prevents macrophage activation, blocks phagosome acidification and maturation, and attenuates presentation of antigens to the immune system. The consequence is a very long silent infection before clinical signs are observed. The present work examined the transcriptome of bovine monocyte-derived macrophages (MDM) infected with the L1 strain of MAP at 2h, 6h and 24h post infection using RNA-seq. Pathway over-representation analysis of genes differentially expressed between infected vs. control MDM identified that immune related pathways were affected. Genes belonging to the cytokine-cytokine receptor interaction pathway and members of the JAK-STAT pathway, which is involved in the regulation of immune response, were up-regulated. However, in parallel inhibitors of immune functions were activated, including suppressor of cytokine signaling (SOCS) and cytokine-inducible SH2-containing protein (CISH), which most likely suppresses IFNγ and the JAK/STAT signaling cascade in infected MDM, which may favour MAP survival. After exposure, macrophages phagocytise pathogens, activate the complement cascade and the adaptive immune system through the antigen presentation process. However, data presented here suggest that genes related to phagocytosis and lysosome function are down regulated in MAP infected MDM. Genes of MHC class II and complement pathway were also down-regulated. This study therefore shows that MAP infection is associated with changes in expression of genes related to the host immune response that may affect its ability to survive and multiply inside the host cell.

Microglia are crucial regulators of neuro-immunity during central nervous system tuberculosis

Mycobacterium tuberculosis (M. tuberculosis) infection of the central nervous system (CNS) is the most devastating manifestation of tuberculosis (TB), with both high mortality and morbidity. Although research has been fueled by the potential therapeutic target microglia offer against neurodegenerative inflammation, their part in TB infection of the CNS has not been fully evaluated nor elucidated. Yet, as both the preferential targets of M. tuberculosis and the immune-effector cells of the CNS, microglia are likely to be key determinants of disease severity and clinical outcomes. Following pathogen recognition, bacilli are internalized and capable of replicating within microglia. Cellular activation ensues, utilizing signaling molecules that may be neurotoxic. Central to initiating, orchestrating and modulating the tuberculous immune response is microglial secretion of cytokines and chemokines. However, the neurological environment is unique in that inflammatory signals, which appear to be damaging in the periphery, could be beneficial by governing neuronal survival, regeneration and differentiation. Furthermore, microglia are important in the recruitment of peripheral immune cells and central to defining the pro-inflammatory milieu of which neurotoxicity may result from many of the participating local or recruited cell types. Microglia are capable of both presenting antigen to infiltrating CD4(+) T-lymphocytes and inducing their differentiation-a possible correlate of protection against M. tuberculosis infection. Clarifying the nature of the immune effector molecules secreted by microglia, and the means by which other CNS-specific cell types govern microglial activation or modulate their responses is critical if improved diagnostic and therapeutic strategies are to be attained. Therefore, this review evaluates the diverse roles microglia play in the neuro-immunity to M. tuberculosis infection of the CNS.

Mycobacteria and biological response modifiers: two sides of the relationship

With increasing use of biological response modifiers (BRMs) for various systemic inflammatory diseases there is a need to be vigilant about complications with the use of these therapies. It is important to have appropriate screening for the infections in patients requiring BRMs. However, many studies have reported benefits of certain BRMs in the treatment of infections such as tuberculosis as adjuncts. Continued research and technical advances in immunogenetics helps understand complex mechanisms in the usage of the BRMs. This article summarizes the different aspects of the relationship between mycobacterial infections and the use of various BRMs for inflammatory conditions.

Extracellular-regulated kinase activation regulates replication of Mycobacterium avium intracellularly in primary human monocytes

Mycobacterium avium-intracellulare (MAI) is a ubiquitous environmental pathogen that causes disseminated infection in immunocompromised patients, such as those with human immunodeficiency virus, interleukin-12 deficiency, or interferon-gamma receptor mutation. Colony morphotypes are associated with MAI pathogenicity. Our previous studies have reported that smooth-transparent (SmT) morphotypes are more virulent and induce less cytokine (interleukin-1beta and tumor necrosis factor-alpha) production by human monocytes than the smooth-domed (SmD) morphotypes. Mitogen-activated protein (MAP) kinases such as extracellular-regulated kinase (ERK) are activated by the phagocytosis of particle antigens in macrophages, and this ERK activation subsequently influences cytokine expression and the control of intracellular pathogen growth. The influence of MAP kinase activation on MAI replication in human monocytes was examined. Peripheral blood monocytes isolated from healthy subjects by Ficoll-Hypaque sedimentation were infected with virulent SmT or avirulent SmD MAI without or with MAP kinase inhibitors. MAP kinase activities were determined by in vitro kinase assay, intracellular MAI growth by CFU assay, and cytokines by enzyme-linked immunosorbent assay. MAI infection induced ERK and p38 activation. Inhibition of ERK by PD98059, but not p38, significantly increased intracellular MAI growth. Tumor necrosis factor-alpha release and interleukin-1beta production in response to MAI were reduced by MAP kinase inhibition. p38 inhibition tended to reduce cytokine production more substantially. These data suggest that ERK activation limits intra-monocytic MAI replication and enhances monocytic cytokine release, whereas p38 activation influences only cytokine release. The effect of MAP kinases on MAI growth might thus be mediated by the modulation of cytokine production.

Pulmonary infection of Mycobacterium avium-intracellulare complex with simultaneous organizing pneumonia

A 67-year-old woman presented high-grade fever and dyspnea. Sputum culture confirmed Mycobacterium avium-intracellulare complex (MAC). Transbronchial lung biopsies revealed organizing pneumonia (OP) that was rapidly improved with corticosteroid. Five months after onset, a nodule emerged in the right lung. Although MAC was confirmed, the lesion was deemed too small to merit anti-mycobacterial chemotherapy. Four months later, diffuse infiltrates developed on chest X-ray. Bronchoalveolar lavage study identified MAC and exhibited OP patterns. We commenced antimycobacterial chemotherapy. The infiltrates almost completely improved within a month without corticosteroid.

Caspase activation may be associated with Mycobacterium avium pathogenicity

BACKGROUND

Mycobacterium avium causes disseminated infection in immunocompromised patients and triggers a process resembling Crohn's disease in goats. Colony morphotypes predict pathogenicity. Smooth-transparent (SmT) morphotypes are more virulent and induce less interleukin (IL)-1beta and IL-18 production than avirulent smooth-domed (SmD) morphotypes. Caspases are essential for IL-1beta and IL-18 production.

METHODS

Caspase activation was examined in human monocytes after M. avium infection.

RESULTS

Fresh monocytes constitutively expressed caspase-1 mRNA and pro-caspase-1. The M. avium infection increased monocyte caspase-1 mRNA expression. Furthermore, SmD-infected monocytes expressed 2.3-fold higher levels (P <0.05, n = 3) of activated caspases than SmT-infected monocytes. Caspase-1 inhibition significantly reduced IL-1beta production by SmT- and SmD-infected monocytes (P <0.05, n = 4). Caspase-3 inhibition inhibited IL-1beta production 43.5% +/- 8.0% (P <0.02, n = 4) by SmD-infected but not SmT-infected monocytes.

CONCLUSIONS

Decreased mature IL-1beta release by SmT-infected monocytes may reflect selective induction of caspase-1 activity but not caspase-3. Differential caspase expression in monocytes after infection may contribute to M. avium pathogenicity in humans.

Mycobacterium avium complex promotes recruitment of monocyte hosts for HIV-1 and bacteria

In lymphoid tissues coinfected with Mycobacterium avium complex (MAC) and HIV-1, increased viral replication has been observed. This study investigates the role of MAC in perpetuating both infections through the recruitment of monocytes as potential new hosts for bacteria and HIV-1. Increased numbers of macrophages were present in the lymph nodes of patients with dual infection as compared with lymph nodes from HIV(+) patients with no known opportunistic pathogens. In a coculture system, monocyte-derived macrophages were treated with HIV-1 or M. avium and its constituents to further define the mechanism whereby MAC infection of macrophages initiates monocyte migration. Monocyte-derived macrophages treated with bacteria or bacterial products, but not HIV-1, induced a rapid 2- to 3-fold increase in recruitment of monocytes. Pretreatment of the monocytes with pertussis toxin inhibited the migration of these cells, indicating a G protein-linked pathway is necessary for induction of chemotaxis and thus suggesting the involvement of chemokines. Analysis of chemokine mRNA and protein levels from M. avium-treated cultures revealed MAC-induced increases in the expression of IL-8, macrophage-inflammatory protein (MIP)-1alpha, and MIP-1beta with donor-dependent changes in monocyte chemotactic protein-1. Pyrrolidine dithiocarbamate, an antioxidant, inhibited the activation of NF-kappaB and significantly diminished the MAC-induced chemotaxis, concurrently lowering the levels of monocyte chemotactic protein-1 and MIP-1beta. These data demonstrate that MAC induces macrophage production of multiple chemotactic factors via NF-kappaB to promote monocyte migration to sites of MAC infection. In vivo, opportunistic infection may act as a recruitment mechanism in which newly arrived monocytes serve as naive hosts for both MAC and HIV-1, thus perpetuating both infections.

Suppression of granulocyte/macrophage colony-stimulating factor release from human monocytes by cyclic AMP-elevating drugs: role of interleukin-10

1. Granulocyte/macrophage colony-stimulating factor (GM-CSF) is a pro-inflammatory cytokine secreted by cells of the monocyte/macrophage lineage and has been implicated in the pathogenesis of bronchitis and asthma. 2. In the present study we have evaluated the effect of several cyclic AMP-elevating agents on lipopolysaccharide (LPS)-induced GM-CSF release from human monocytes and the extent to which the anti-inflammatory cytokine, interleukin (IL)-10, is involved. 3. LPS evoked a concentration-dependent generation of GM-CSF from human monocytes that was inhibited, at the mRNA and protein level, by 8-Br-cyclic AMP, cholera toxin, prostaglandin E2 (PGE2) and a number of structurally dissimilar phosphodiesterase (PDE) 4 inhibitors. 4. Pre-treatment of monocytes with a concentration of an anti-IL-10 monoclonal antibody that abolished the inhibitory action of a maximally effective concentration of exogenous human recombinant IL-10, significantly augmented LPS-induced GM-CSF generation. This effect was associated with a parallel upwards displacement of the concentration-response curves that described the inhibition of GM-CSF by PGE2, 8-Br-cyclic AMP and the PDE4 inhibitor, rolipram, without significantly changing the potency of any drug. Consequently, the maximum percentage inhibition of GM-CSF release was reduced. Further experiments established that the reduction in the maximum inhibition of GM-CSF release seen in anti-IL-10-treated cells was not due to functional antagonism as rolipram, PGE2 and 8-Br-cyclic AMP were equi-effective at all concentrations of LPS studied. 5. These data indicate that cyclic AMP-elevating drugs attenuate the elaboration of GM-CSF from LPS-stimulated human monocytes by a mechanism that is not mediated via IL-10. Suppression of GM-CSF from monocytes may explain, at least in part, the efficacy of PDE4 inhibitors in clinical trials of chronic obstructive pulmonary disease.

Treatment of infections in the patient with Mendelian susceptibility to mycobacterial infection

Cytokines are increasingly used for the therapy of infections in patient populations with special defects in immunity (chemotherapy, bone marrow transplantation, chronic granulomatous disease). The recognition of multiple defects in the systems of the interferon-gamma (IFN-gamma) receptor, interleukin-12 (IL-12) receptor and IL-12 p40 emphasizes the critical roles that cytokines play in preventing and clearing infection. The cases of patients with partially responsive IFN-gamma receptors (autosomal dominant and partial defects) are ideal candidates for successful cytokine prophylaxis and therapy. Better understanding of the critical elements of the cytokine pathways may show us ways to circumvent these defects with complementary cytokine cascades.

p38 MAP kinase and MKK-1 co-operate in the generation of GM-CSF from LPS-stimulated human monocytes by an NF-kappa B-independent mechanism

1. The extent to which the p38 mitogen-activated protein (MAP) kinase and MAP kinase kinase (MKK)-1-signalling pathways regulate the expression of granulocyte/macrophage colony-stimulating factor (GM-CSF) from LPS-stimulated human monocytes has been investigated and compared to the well studied cytokine tumour necrosis factor-alpha (TNF alpha). 2. Lipopolysaccharide (LPS) evoked a concentration-dependent generation of GM-CSF from human monocytes. Temporally, this effect was preceded by an increase in GM-CSF mRNA transcripts and abolished by actinomycin D and cycloheximide. 3. LPS-induced GM-CSF release and mRNA expression were associated with a rapid and time-dependent activation of p38 MAP kinase, ERK-1 and ERK-2. 4. The respective MKK-1 and p38 MAP kinase inhibitors, PD 098059 and SB 203580, maximally suppressed LPS-induced GM-CSF generation by >90%, indicating that both of these signalling cascades co-operate in the generation of this cytokine. 5. Electrophoretic mobility shift assays demonstrated that LPS increased nuclear factor kappa B (NF-kappa B) : DNA binding. SN50, an inhibitor of NF-kappa B translocation, abolished LPS-induced NF-kappaB : DNA binding and the elaboration of TNFalpha, a cytokine known to be regulated by NF-kappaB in monocytes. In contrast, SN50 failed to affect the release of GM-CSF from the same monocyte cultures. 6. Collectively, these results suggest that the generation of GM-CSF by LPS-stimulated human monocytes is regulated in a co-operative fashion by p38 MAP kinase- and MKK-1-dependent signalling pathways independently of the activation of NF-kappa B.

Effect of poloxamer CRL-1072 on drug uptake and nitric-oxide-mediated killing of Mycobacterium avium by macrophages

Mycobacterium avium-intracellulare complex (MAI) are common pathogens of opportunistic infections that are naturally resistant to most antibiotics and develop acquired resistance rapidly. An experimental drug, poloxamer CRL-1072, was found to have two unusual properties: it synergistically enhanced the activity of several antibiotics against MAI even though it had little activity as a single agent and it had greater activity against MAI in macrophage culture or in mice than in broth culture. Studies were undertaken to investigate the mechanisms of these effects. CRL-1072 was taken up by MAI and enhanced the uptake of fluorescent-labeled streptomycin and erythromycin in broth culture. The labeled antibiotics had reduced activity so the relevance for naive antibiotics must be inferred. In culture with human U937 monocytoid cells, CRL-1072 became localized in phagosomes and promoted uptake of streptomycin. Finally, CRL-1072 was found to induce production of mRNA for inducible nitric oxide synthase (iNOS) and nitric oxide (NO) by U937 cells. The antimycobacterial effect in macrophages was reversed by the iNOS inhibitor N-monomethyl L-arginine (NMMA), suggesting that CRL-1072 promotes killing of MAI by inducing NO. These effects were induced by noncytotoxic concentrations of CRL-1072. These data suggest that the antimycobacterial mechanisms of CRL-1072 include enhancing the delivery of antibiotic to targets within MAI and enhancement of the ability of macrophages to kill ingested organisms.

Exposure of human peripheral blood mononuclear cells to total lipids and serovar-specific glycopeptidolipids from Mycobacterium avium serovars 4 and 8 results in inhibition of TH1-type responses

Previous studies have suggested that large quantities of bacterial lipids may accumulate and persist within host cells during chronic stages of Mycobacterium avium infections. This study intended to assess the ability of purified M. avium lipids to affect TH-1-type responses in human peripheral blood mononuclear cells (PBMC) from healthy donors. PBMC were exposed to total lipids and serovar-specific glycopeptidolipids (GPL) extracted from M. avium serovars 4 and 8, which have been reported to predominate as opportunistic infection among AIDS patients. After 24 h exposure to lipids followed by PHA/PMA treatment, IL-2 and IFN-gamma were assayed in the supernatants. Reverse transcriptase polymerase chain reaction (RT-PCR) was used for a semiquantitative estimation of mRNA for IL-2 and IFN-gamma in cell pellets at various time points. Exposure of PBMC to M. avium total lipids significantly suppressed PHA/PMA-induced secretion of IL-2 and IFN-gamma as determined by ELISA. The GPL antigens from serovar 4 were more efficient at inhibiting TH-1 responses than GPL from serovar 8. CD4(+)T-lymphocyte enrichment of PBMC demonstrated that suppression by M. avium lipids was intact without the presence of other cell populations such as monocytes and B-cells. Preliminary RT-PCR experiments showed that the secretion of TH-1 cytokines was partially affected at the transcriptional level. The results obtained showed that M. avium lipids are indeed able to modify the induction of TH-1-type cytokines by human PBMC, and suggest that accumulation of M. avium lipids in the chronic stages of infection may play an important role in the pathogenesis of HIV infection.

Role of cytokines in pulmonary antimicrobial host defense

Host defense of the lung is characterized by a fine balance between the generation of a vigorous inflammatory response to clear pathogens and maintenance of the integrity of the alveolar gas-exchange surface. The magnitude of the inflammatory response is therefore tightly regulated by pro- and anti-inflammatory cytokine mediators. This article summarizes current information on the roles of specific cytokines in pneumonia, with particular emphasis on ongoing investigations into the role of innate immunity in bacterial and fungal pneumonia.

Immunological defense mechanisms in tuberculosis and MAC-infection

Protective immunity to mycobacterial infections develops in immunocompetent hosts after activation of alpha beta- and gamma delta-T cells in association with the generation of a protection-specific cytokine profile that stimulates the bactericidal potential of the macrophages. The maintenance of a delicate balance between Th1 and Th2 response is decisive for infection control and prevention of exacerbation of disease. Mycobacterial infection in the immunocompromised host is mainly due to the diminished cellular immune function. In addition, nontuberculous mycobacteria isolated from AIDS patients have special virulence factors that promote development of disease by further compromising the function of an already damaged cytokine network.

Effect of stimulation of human macrophages on intracellular survival of Mycobacterium bovis Bacillus Calmette-Guerin. Evaluation with a mycobacterial reporter strain

The mechanisms through which immune and inflammatory responses stimulate the expression of antimycobacterial activity by human macrophages remain poorly defined. To study this question, we developed a method permitting the rapid quantification of viable mycobacteria, based on the detection of luciferase activity expressed by a Mycobacterium bovis Bacillus Calmette-Guerin (BCG) reporter strain, and used this approach to evaluate mycobacterial survival in human monocyte-derived macrophages following stimulation with cytokines and through crosslinking of costimulatory molecules expressed on the cell surface. Modest proliferation, followed by persistence of mycobacteria, was observed in unpretreated macrophages as assessed both by measurement of luciferase activity and by the evaluation of colony forming units. Of the 19 cytokines tested, only granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) were found to improve the mycobactericidal activity of monocyte-derived macrophages. In both cases, this effect was observed only when macrophages were pretreated with the cytokines prior to infection. In contrast, pretreatment of human macrophages with interferon-gamma, either alone or in combination with other mediators (including tumor necrosis factor-alpha and 1,25[OH]2-vitamin D3), did not improve mycobacterial killing. The stimulation of macrophages through several different costimulatory molecules known to participate in macrophage-lymphocyte interactions (CD4, CD40, CD45, CD86, CD95 [Fas/Apo-1]) also failed to improve mycobactericidal activity. This study shows that GM-CSF and IL-3, cytokines whose receptors are known to share a common subunit and to use common second messengers, may contribute to the stimulation of mycobactericidal activity in humans. The ability to rapidly screen the effects of different macrophage stimuli on mycobacterial survival through the detection of luciferase activity should help define additional signals required for optimal antimycobacterial responses.

Retrospective analysis of infectious disease in patients who received recombinant human granulocyte-macrophage colony-stimulating factor versus patients not receiving a cytokine who underwent autologous bone marrow transplantation for treatment of lymphoid cancer

Recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) significantly shortens the number of days required to achieve an absolute neutrophil count of >500/mm3 after autologous bone marrow transplantation (ABMT); however, the ability of rhGM-CSF to enhance neutrophil and macrophage function in vivo has been incompletely characterized. In this retrospective study, the authors compared the incidence of infection from the day of transplantation to 28 days posttransplantation between two groups of previously studied patients who underwent ABMT at the Fred Hutchinson Cancer Research Center. A control group that received no cytokine was compared with a study group that received rhGM-CSF while participating in phase I, II, or III trials. During the posttransplantation period when both study groups had severe neutropenia, 40% (38 of 95) of control patients were found to have an infection, whereas only 13% (6 of 46) of rhGM-CSF patients developed an infection (p = 0.001). Most infections occurred before an absolute neutrophil count of > 100/mm3 was achieved. There was a trend toward fewer fungal infections (14% vs. 4%; p = 0.093); gram-negative bacterial infections (6% vs. 0%; p = 0.083); pulmonary infections (12% vs. 2%; p = 0.062); fewer days of amphotericin B (p = 0.0305); and fewer days of intravenous antibiotics (p = 0.0791) in rhGM-CSF-treated patients. These results support in vivo findings that the function-enhancing effect of rhGM-CSF may reduce infection-related complications.

Comparison of neutrophil and monocyte function by microbicidal cell-kill assay in patients with cancer receiving granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, or no cytokine after cytotoxic chemotherapy: a phase II trial

Functional effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) and recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) were prospectively measured by harvesting blood samples from 51 oncology patients (21 who were receiving no cytokines, 14 receiving rhGM-CSF, and 16 who were receiving rhG-CSF) just before cytotoxic chemotherapy (baseline) immediately before the last cytokine dose (pre), 2 hours after the last cytokine dose (post), and 48 hours after the pre period (follow-up). Neutrophils and monocytes were separated and functional effects were measured by comparing cell-kill percentages, as determined by a microbial cell-kill assay against Staphylococcus aureus and Candida albicans. Optimal cell concentrations (2 x 10(6) monocytes/ml; 4 x 10(6) neutrophils/ml) and effector-to-cell ratios (1:50) were initially determined with blood samples harvested from 23 healthy volunteers. Results in oncology patients indicated that rhGM-CSF improved monocyte-killing activity against S. aureus at follow-up, compared with controls (p = 0.0094) and compared with monocytes from rhG-CSF-treated patients at the post period (p = 0.014). Cell-killing percentage of the rhGM-CSF-treated patients was also enhanced against C. albicans during the post period, compared with controls (p = 0.011) and rhG-CSF-treated patients (p = 0.067). Neutrophil activity was not altered by either cytokine. In conclusion, monocyte-induced microbial killing was enhanced in oncology patients receiving rhGM-CSF after cytotoxic chemotherapy, compared with patients receiving rhG-CSF or no cytokines. No differences in neutrophil activity were observed between patients receiving either cytokine.

Induction of gamma interferon production in human alveolar macrophages by Mycobacterium tuberculosis

Gamma interferon (IFN-gamma) is a cytokine which plays a critical role in resistance to Mycobacterium tuberculosis infection. While T lymphocytes and natural killer cells are a major source of IFN-gamma, previous demonstrations that it can be produced by murine macrophages prompted us to examine the capacity of human alveolar macrophages to express IFN-gamma. Here we report that in vitro infection of alveolar macrophages with M. tuberculosis induces both the release of IFN-gamma protein and a transient increase in IFN-gamma mRNA levels. The IFN-producing cells were shown to be macrophages by reverse transcription-in situ PCR. We also observed that M. tuberculosis stimulation resulted in IFN-gamma-dependent expression of the chemokines IFN-gamma-inducible protein 10 and monokine induced by IFN-gamma, suggesting that macrophage-derived IFN-gamma can function in an autocrine and/or paracrine manner. The existence of a positive regulatory loop was suggested by the observation that exogenous IFN-gamma protein could induce IFN-gamma mRNA expression in uninfected alveolar macrophages. Interleukin-12 was also found to be a potent inducer of IFN-gamma production, and M. tuberculosis-induced IFN-gamma production appears to be mediated, at least in part, by IL-12. In contrast, M. tuberculosis-induced IFN-gamma production by alveolar macrophages could be blocked by exogenous interleukin-10. These studies are the first to demonstrate an autoregulatory role for IFN-gamma produced by alveolar macrophages infected in vitro with M. tuberculosis.

Altered IL-1 expression and compartmentalization in monocytes from patients with AIDS stimulated with Mycobacterium avium complex

The pathophysiologic basis for the exuberant intracellular growth of Mycobacterium avium complex (MAC) in AIDS patients is unclear but may relate to altered expression of modulatory cytokines. Interleukin (IL)-1, IL-6, and TNF-alpha expression by monocytes from AIDS patients and healthy subjects (HS) stimulated with isogeneic MAC strains (SmT, smooth-transparent, virulent; SmD, smooth-domed, avirulent) was examined. Spontaneous cytokine production was not observed in patients with AIDS. MAC strains induced less IL-1 alpha and IL-1 beta release in AIDS patients than HS (P < 0.05). The ratio of cell-associated to supernatant IL-1 alpha also was increased in AIDS patients (P = 0.03). IL-1 beta mRNA expression paralleled protein release in either group of subjects. In both HS and AIDS patients, stimulation with SmD induced more IL-1 and TNF-alpha release by monocytes compared to SmT. In AIDS patients, SmD also induced greater IL-6 release than SmT (P < 0.01). Alterations in monocyte expression and compartmentalization of the regulatory cytokines IL-1 and IL-6 may enhance bacterial replication and contribute to the pathogenesis of MAC infection in AIDS.

Differential effects of granulocyte/macrophage colony-stimulating factor (GM-CSF) in enhancing macrophage resistance to Legionella pneumophila vs Candida albicans

It has been reported that granulocyte/macrophage colony-stimulating factor (GM-CSF), one of the hemopoietic growth factors which regulates the function of phagocytic cells, is a potent activator of cultured macrophages and induces antimicrobial activities as well as differentiation of precursor cells. In this study, we examined the ability of recombinant murine GM-CSF to activate mouse peritoneal macrophages to restrict the growth of two different microorganisms, Candida albicans and Legionella pneumophila, both of which are important opportunistic pathogens in an immunocompromised host. Treatment of thioglycollate-elicited BDF1 mouse macrophages with GM-CSF for 24 hr enhanced the anti-C. albicans activity of the macrophages in terms of inhibiting growth of the fungi. Reactive oxygen (H2O2) and IL-1 production by the macrophages were also enhanced by treatment with GM-CSF. However, no enhancement of anti-L. pneumophila activity of macrophages obtained from either susceptible A/J or resistant BDF1 mice to L. pneumophila infection after treatment with up to 1000 units/ml GM-CSF was observed under the same conditions. When the treatment time was extended to 72 hr. GM-CSF was still unable to induce anti-L. pneumophila activity. As a control study, treatment with recombinant IFN-gamma enhanced both anti-Candida and anti-Legionella activity in cultured macrophages under the same conditions used in the GM-CSF study. Measurement of cellular iron content revealed the low iron content in IFN-gamma-treated macrophages, but no decrease of iron in GM-CSF-treated macrophages compared with the control group, indicating a possible involvement of iron as a key factor in anti-L. pneumophila activity. Thus, the results of the study show that GM-CSF activation of elicited peritoneal macrophages is selective with regard to the type of antimicrobial activity induced.

Lack of in vivo effect of granulocyte-macrophage colony-stimulating factor on human immunodeficiency virus type 1

Neutropenia complicates HIV disease or its treatment in a large proportion of patients. Hematopoietic growth factor support has been tested in a number of clinical settings in HIV disease and has been demonstrated to be of benefit for specific parameters. One consideration regarding the use of hematopoietic growth factors in HIV disease is their potential effect on HIV viral burden, since alterations in HIV expression have been documented with certain cytokines in vitro. It has also been reported that some cytokines, notably GM-CSF, potentiate the antiviral properties of thymidine analogs such as zidovudine (AZT) in vitro. We tested these observations in vivo. Twelve HIV-positive patients with a CD4 cell count < or = 200/mm3 or HIV plasma viremia who were receiving a stable dose of zidovudine were enrolled into three dose cohorts of yeast-derived GM-CSF at 50, 125, or 250 micrograms/m2 daily by subcutaneous self-injection for 28 days. Measurements of HIV activity included serum acid-dissociated HIV p24 antigen levels, plasma and peripheral blood mononuclear cell (PBMC) limiting dilution HIV culture, and plasma HIV quantitative competitive polymerase chain reaction (PCR). Serum and intracellular zidovudine levels were measured as well as hematologic, immunologic, and toxicity parameters. Virologic measures showed neither significant upregulation nor downregulation of serum acid-dissociated HIV p24 antigen, plasma and PBMC HIV culture, or PCR in association with GM-CSF administration. A trend toward increased intracellular AZT levels was noted, but this did not achieve statistical significance (p = 0.073). CD4 and CD8 lymphocytes were essentially unaffected while absolute neutrophil counts increased with GM-CSF administration as expected. These data suggest that administration of GM-CSF does not perturb HIV activity or immunologic parameters in patients receiving AZT for advanced HIV disease. No potentiation of AZT antiviral effect was demonstrated.

Macrophage release of tumor necrosis factor-alpha by Mycobacterium avium antigens

Mycobacterium avium complex (MAC) infection is the most common disseminated opportunistic infection encountered in patients with AIDS. We have studied the ability of specific Mycobacterium avium (MA) antigen to stimulate human monocyte-derived macrophages (MDM) to produce tumor necrosis factor-alpha (TNF-alpha). MDM stimulated with MA sonicate, MA 68 kDa and MA 48-52 kDa antigens were found to produce TNF-alpha in a dose-dependent manner. Reverse transcriptase-polymerase chain reaction analysis of mRNA extracts from antigen-stimulated MDM indicated that TNF-alpha mRNA expression was of brief duration and the time point of peak TNF-alpha mRNA levels was found to be antigen-specific. A significant difference in TNF-alpha production in response to MA 48-52 kDa antigen and M. bovis 65 kDa antigen was observed between MDM from normal and HIV positive individuals.

The role of tumour necrosis factor-alpha in combination with interferon-gamma or interleukin-1 in the induction of immunosuppressive macrophages because of Mycobacterium avium complex infection

The role of some cytokines including tumour necrosis factor-alpha (TNF-alpha), interleukin-1 alpha (IL-1 alpha), interferon-gamma (IFN-gamma), transforming growth factor-beta (TGF-beta) and interleukin-6 (IL-6) in the generation of immunosuppressive macrophages (M phi s) in host spleen cells of Mycobacterium avium complex (MAC)-infected mice was studied. M phi populations with potent suppressor activity against concanavalin A (Con A)-induced mitogenesis of splenocytes (SPCs) were elicited not only in euthymic but also in athymic nude mice during MAC infection. The suppressor M phi s are, therefore, inducible not only through a T-cell-dependent mechanism but also through T-cell-independent mechanism. However, MAC-induced M phi s of athymic mice displayed about four times lower suppressor activity than those of euthymic mice, indicating that mature T cells are important for M phi activation to the highly immunosuppressive state. Anti-TNF, anti-IFN-gamma, and anti-TGF-beta antibodies (Abs) but not anti-IL-6 Ab inhibited in vivo generation of MAC-induced immunosuppressive M phi s, and the neutralizing efficacy was in the order of anti-IFN-gamma Ab > anti-TNF Ab > anti-TGF-beta Ab. The effects of TNF-alpha, IL-1 alpha, IL-6, and IFN-gamma alone or combinations of them upon the acquisition of the suppressor activity by cultured splenic M phi s were studied. When normal splenic M phi s were treated with each cytokine for 3 days, TNF-alpha, IFN-gamma, and IL-1 alpha alone caused a slight elevation of their suppressive activity. Treatment of the normal M phi s with the combination of either TNF-alpha+IL-1 alpha or TNF-alpha+IFN-gamma yielded a marked increase in the suppressor activity, followed by IL-1 alpha+IFN-gamma. These findings indicate the important roles of TNF-alpha, IFN-gamma, and IL-1 alpha in the generation of MAC-induced suppressor M phi s.

Susceptibility of beige mice to Mycobacterium avium: role of neutrophils

The beige mutation in C57BL/6 mice has been shown to increase the susceptibility to infection by Mycobacterium avium. In this study, we confirmed those results and showed that the effect of the beige mutation was most obvious after infection with a strain of lower virulence than with a highly virulent isolate of M. avium. The dissemination of M. avium from the gut was observed with both C57BL/6 and beige mice but was faster in the latter. The expression of gamma interferon (IFN-gamma) and the priming for tumor necrosis factor production during an in vivo infection were similar between beige and immunocompetent C57BL/6 mice. IFN-gamma produced during the infection of beige mice was protective in the spleen, and the administration of recombinant IFN-gamma restored the resistance in the spleen to levels similar to those found in control mice. There were no histological differences between wild-type and beige mice with respect to granuloma formation in the liver. The increased susceptibility of beige mice to M. avium as manifested in the liver was reduced by transfusing neutrophils from wild-type C57BL/6 mice. Likewise, depletion of neutrophils from C57BL/6 mice rendered them as susceptible to M. avium infection of the liver as beige mice. Our results point to the participation of neutrophils in the defect of beige mice in addition to other defects. Furthermore, these results show that neutrophils play a significant role in the defense mechanisms against mycobacterial infections and that beige animals may be a useful model for study of the role of neutrophils in mycobacteriosis.

Mycobacterium avium complex: advances in therapy

Disseminated Mycobacterium avium complex (MAC) is one of the most common opportunistic infections in AIDS patients and is increasingly recognized as a significant pathogen in chronic pulmonary disease in nonimmunocompromised patients. Important progress in therapy has occurred over the last several years. In AIDS patients, multidrug therapy has been shown to be beneficial in terms of reducing circulating bacteremia and improving clinical symptoms. Clarithromycin and azithromycin, two broad-spectrum antimicrobials with minimal activity against Mycobacterium tuberculosis, have emerged as potent, well tolerated agents pivotal to treatment regimens. In AIDS patients, rifabutin prophylaxis reduced the frequency of MAC bacteremia by 50% in two placebo controlled trials. Despite these advances, there remains a need for determining the optimal combination regimens for therapy, and more effective drugs for prophylaxis which are beneficial both in terms of survival and functional capacity of patients.

Endogenous production and peripheral blood levels of granulocyte-macrophage (GM-) and granulocyte (G-) colony-stimulating factors

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) are two important granulopoietic growth factors. This review will focus on the endogenous production of human GM-CSF and human G-CSF and its possible reflection in circulating levels in peripheral blood. When adequately stimulated a variety of cell-types such as monocytes/macrophages. T-lymphocytes, endothelial cells and fibroblasts can produce CSFs in vitro. G-CSF can increase to detectable levels in peripheral blood when there is a demand for granulocyte production such as acute neutropenic in conjunction with hematological disorders, chronic neutropenic conditions and acute infectious diseases in patients with or without underlying hematological disorders. G-CSF in peripheral blood is detected more often and in higher concentrations than GM-CSF. An independent regulation of GM-CSF and G-CSF secretion, quantitative differences in production and/or differences in elimination or distribution might be of importance.

Effector mechanisms involved in cytokine-mediated bacteriostasis of Mycobacterium avium infections in murine macrophages

In this study we found that addition of a range of doses of interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), or granulocyte-macrophage colony stimulating factor (GM-CSF) to cultures of bone marrow-derived murine macrophages infected with the 25291 strain of Mycobacterium avium gave rise to varying degrees of bacteriostasis. In contrast, similar treatment with interleukin-4 (IL-4) or IL-6 had no effect. However, when similar experiments with the former set of cytokines were performed using a panel of M. avium isolates, substantial isolate-to-isolate variation was observed. In cultures containing IFN-gamma, synthesis of substantial levels of reactive nitrogen intermediates was observed; however, neither these materials, nor reactive oxygen intermediates, were found to be responsible for observed bacteriostasis. In further experiments, in which the culture medium was supplemented with various concentrations of a weak acid or a weak base in order to influence the pH of macrophage intracellular compartments, it was found that the presence of the weak acid augmented the activity of IFN-gamma, whilst the weak base counteracted this effect. These data support the hypothesis, therefore, that the bacteriostatic effect of IFN-gamma against the growth of M. avium, rather than depending on reactive radical production, is mediated through acidification of the infected phagosome, perhaps through activation of proton pumps in the phagosomal membrane.

Increased C3 production in human monocytes after stimulation with Candida albicans is suppressed by granulocyte-macrophage colony-stimulating factor

Activation of the complement system is an important part of host resistance against fungal infections. When human monocytes, cultured for 2 days or more, were treated in vitro with Candida albicans for 24 h, an enhancement of their biosynthesis of the complement components C3 and factor B was found. However, when C. albicans was administered to freshly isolated monocytes, a consistent stimulation of factor B biosynthesis occurred, while the C3 production was increased in about 50% of the donors. C. albicans also induced the release of granulocyte-macrophage colony-stimulating factor (GM-CSF) from the cultured cells, apparently in larger amounts in the donors in whom no stimulation of C3 production was found. An antibody to GM-CSF administered with the yeast at the initiation of the monocyte culture caused an increase in the C3 production. Furthermore, when monocytes were treated with recombinant human GM-CSF either at the same time as or 4 days prior to the addition of C. albicans, the increase in C3 production was suppressed or neutralized, while factor B biosynthesis was unaffected. Taken together, these results indicate that monocytes respond to C. albicans with an increased production of complement factors. This may be an important mechanism both for opsonization of the fungus and for initiation of an inflammatory reaction. At an inflammatory site, this complement response may be suppressed by locally produced GM-CSF.

Inhibition of growth of Mycobacterium avium in murine and human mononuclear phagocytes by migration inhibitory factor

Infections caused by Mycobacterium avium, the most common form of diseminated bacterial disease in AIDS patients, are difficult to treat because of their resistance to many antimycobacterial drugs. The results of the present study show that recombinant migration inhibitory factor, a 12-kDa molecule recently isolated by COS-1 cell expression screening of cDNA from a human T-cell hybridoma, has potent inhibitory activity on the growth of a panel of clinical isolates of M. avium within both bone-marrow-derived murine macrophages and cultured human blood monocytes. These cells cultured in recombinant migration inhibitory factor exhibit various signs of activation, including cell division, morphological changes such as evidence of substantial phagolysosomal fusion, and enhanced secretion of tumor necrosis factor.

A comparison of the different methods available for determining BCG-macrophage interactions in vitro, including a new method of colony counting in broth

Different methods of determining BCG viability based on colony forming unit (CFU) counting and radio-isotope labelling were comparatively assessed. These included radio-isotope labelling with [3H]uracil, [3H]uridine, [3H]glycerol, and CFU counting, by both agar plate dilution, and microcolony counting in broth. The sensitivity ranges of the different techniques were determined in both macrophage-free and macrophage-treated systems and used to assess the anti-mycobacterial potential of human monocyte-derived macrophages following BCG infection.

Lymphokine-activated killer cell regulation of T-cell-mediated immunity to Candida albicans

Monocytes are important accessory cells in the activation of T cells for specific antigen recognition yet little is known of their regulation. We demonstrated here that interleukin-2 (IL-2)-induced human lymphokine-activated killer (LAK) cells can inhibit monocyte antigen presentation, depending on the state of differentiation of the monocytes. Adherent monocytes cultured for 4 days in medium or granulocyte-macrophage colony-stimulating factor (GM-CSF) were found to equally process and present intact Candida albicans to autologous Percoll gradient-isolated T cells, as measured by [3H]thymidine uptake. However, only the GM-CSF-cultured monocytes were functionally inhibited by autologous 4-day IL-2-induced LAK cells. Even soluble candidal cell wall mannoprotein antigens could not be presented by these monocytes after exposure to LAK cells. Pretreatment of these monocytes with LAK cells for 1 h, followed by subsequent removal of the nonadherent LAK cells, was sufficient to cause significant inhibition, with maximal inhibition observed after 4 h. Northern (RNA) blot analysis indicated that mRNA expression for IL-1 alpha and IL-1 beta in response to C. albicans stimulation was also down-regulated in GM-CSF-cultured monocytes exposed to LAK cells. Interestingly, freshly isolated, Percoll gradient-purified large granular lymphocytes did not suppress antigen presentation in GM-CSF-treated monocytes. Another important finding was the inability of LAK cells to suppress the ability of freshly isolated or gamma interferon-cultured monocytes, which are resistant to LAK cell-mediated lysis, to present antigen to T cells. In contrast, IL-3 was similar to GM-CSF in inducing LAK cell susceptibility in monocytes. Taken together, these results indicated that IL-2 can induce LAK cells to down-regulate antigen presentation function in a select set of monocytes that have been activated by colony-stimulating factor (GM-CSF and IL-3) but not by gamma interferon. LAK cells may therefore play an important role in regulation of monocytes and their function, depending on their differentiation state.

Mycobacterial induction of activated killer cells: possible role of tyrosine kinase activity in interleukin-2 receptor alpha expression

Mycobacterium avium is an intracellular opportunistic pathogen commonly seen in AIDS patients. M. avium-infected monocytes have been recently shown to be lysed by interleukin-2 (IL-2)-activated killer cells. Since some bacterial products can directly augment natural killer activity, we examined the ability of these microorganisms to induce killer cell activity. Coculture of M. avium with large granular lymphocytes (LGL) was found to augment the ability of LGL to lyse both tumor cells and bacterially infected autologous monocytes. The induction of tumoricidal activity by M. avium was only partially neutralized by the presence of anti-IL-2 antibodies, indicating that both IL-2-dependent and IL-2-independent mechanisms are responsible for activation of killer cells. Furthermore, only the direct interaction between bacterium and LGL could induce the expression of both IL-2 receptor alpha protein and mRNA, an effect which was abrogated by the presence of genistein, a tyrosine kinase inhibitor. Thus, M. avium was seen to induce killer cells, an activity that is concomitant with the up-regulation of IL-2 receptor alpha, or Tac antigen, expression and which involves signal transduction mechanisms mediated by tyrosine kinase activity.

The role of GM-CSF in infection

GM-CSF is a hemopoietic growth factor with substantial effects on the proliferation of neutrophils, eosinophils and monocytes/macrophages. Its physiologic role in infection is still poorly understood. The gene for GM-CSF is constitutively transcribed in cells substantial for antiinfectious response. Various cells are activated and induced by TNF and IL-1 to synthesize GM-CSF. No systemic GM-CSF levels can be detected in patients with infection. It is likely that GM-CSF plays its physiological role in the immediate vicinity of the cells by which it is secreted. GM-CSF functionally activates neutrophils, monocytes/macrophages and eosinophils. It may augment T-cell proliferation and function. GM-CSF is effective in mice infected with Staphylococcus aureus or Salmonella typhimurium. Its effect in infectious disease in man should be explored.