Roles of tumor necrosis factor alpha, granulocyte-macrophage colony-stimulating factor, platelet-activating factor, and arachidonic acid metabolites in interleukin-1-induced resistance to infection in neutropenic mice

Divergent effects of tumor necrosis factor (TNF) in sepsis: a meta-analysis of experimental studies

INTRODUCTION

Experimental studies in animals have yielded conflicting results on the role of Tumor Necrosis Factor (TNF) in sepsis and endotoxemia, with some reporting adaptive and others inappropriate effects. A meta-analysis of the available literature was performed to determine the factors explaining this discrepancy.

METHODS

The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The protocol was registered with PROSPERO (CRD42020167384) prior to data collection. PubMed and Embase were the databases queried. Risk of bias was evaluated using the SYRCLE Risk of Bias Tool. All animal studies investigating sepsis-related mortality and modified TNF signaling were considered eligible. The exclusion criteria were: lack of mortality data, 7-day mortality rates below 10% in both wild type and TNF-altered pathway animals, and absence of an English abstract. To determine the role of TNF according to the experimental protocol, three approaches were used: first an approach based on the statistical significance of each experiment, then the pooled mortality was calculated, and finally the weighted risk ratio for mortality was assessed.

RESULTS

A total of 175 studies were included in the analysis, comprising a total of 760 experiments and involving 19,899 animals. The main species used were mice (77%) and rats (21%). The most common method of TNF pathway modulation was TNF pathway inactivation that was primarily associated with an inappropriate secretion of TNF. At the opposite, TNF injection was associated with an adaptive role of TNF. Lipopolysaccharide (LPS) injection was the most used stimulus to establish an infectious model (42%) and was strongly associated with an inappropriate role of TNF. Conversely, live bacterial models, especially the cecal ligation and puncture (CLP) model, pneumonia, meningitis, and gastrointestinal infection, were associated with an adaptive role. This was particularly evident for Listeria monocytogenes, Streptococcus pneumoniae.

CONCLUSION

The role of TNF during infection varies depending on the experimental model used. Models that mimic clinical conditions, based on virulent bacteria that cause high mortality even at low inocula, demonstrated an adaptive role of TNF. Conversely, models based on LPS or low-pathogenic live bacteria, administered at doses well above physiological thresholds and combined with early antibiotic therapy, were associated with an inappropriate role.

Improvement of Myelopoiesis in Cyclophosphamide-Immunosuppressed Mice by Oral Administration of Viable or Non-Viable Lactobacillus Strains

Myelosuppression is the major dose-limiting toxicity of cancer chemotherapy. There have been many attempts to find new strategies that reduce myelosuppression. The dietary supplementation with lactic acid bacteria (LAB) improved respiratory innate immune response and the resistance against respiratory pathogens in immunosupressed hosts. Although LAB viability is an important factor in achieving optimal protective effects, non-viable LAB are capable of stimulating immunity. In this work, we studied the ability of oral preventive administration of viable and non-viable Lactobacillus rhamnosus CRL1505 or L. plantarum CRL1506 (Lr05, Lr05NV, Lp06V or Lp06NV, respectively) to minimize myelosuppressive and immunosuppressive effects derived from chemotherapy. Cyclophosphamide (Cy) impaired steady-state myelopoiesis in lactobacilli-treated and untreated control mice. Lr05V, Lr05NV and Lp06V treatments were the most effective to induce the early recovery of bone marrow (BM) tissue architecture, leukocytes, myeloid, pool mitotic and post-mitotic, peroxidase positive, and Gr-1^Low/High cells in BM. We selected the CRL1505 strain for being the one capable of maintaining its myelopoiesis-enhancing properties in its non-viable form. Although the CRL1505 treatments do not modify the Cy ability to induce apoptosis, both increased the incorporation of BrdU in BM cells. Consequently, Lr05NV and Lr05V treatments were able to promote early recovery of LSK cells (Lin^-Sca-1⁺c-Kit⁺ cells), multipotent progenitors (Lin^-Sca-1⁺c-Kit⁺CD34⁺ cells), and myeloid cells (Gr-1⁺Ly6G⁺Ly6C^- cells) with respect to the untreated Cy control. In addition, these treatments were able to increase the frequency of IL17A-producing innate lymphoid cells in the intestinal lamina propria (IL-17A⁺RORγt⁺CD4^-NKp46⁺ cells) after Cy injection. These results were correlated with an increase in the IL-17A serum levels, a GM-CSF high expression and a CXCL12 lower expression in BM. Therefore, both Lr05V and Lr05NV treatments are able to activate beneficially the IL-17A/GM-CSF axis and accelerate the recovery of Cy-induced immunosuppression by increasing BM myeloid precursors. We demonstrated for the first time the beneficial effect of CRL1505 strain on myelopoiesis affected by a chemotherapeutic drug. Furthermore, Lr05NV could be a good and safe resource for reducing chemotherapy-induced leukopenia. The results are a starting point for future research and open up broad prospects for future applications of the immunobiotics.

The role of the interleukin-1 family in trained immunity

Immunological memory was long considered a trait exclusive to cells of the adaptive immune system. However, recent studies have shown that after activation of the innate immune system, innate immune cells may undergo long-term functional reprogramming characterized by the ability to mount either a stronger or attenuated inflammatory response upon reactivation. This phenomenon, which has been termed trained immunity and is a de facto innate immune memory, is regulated by a network of integrated metabolic and epigenetic rewiring. The endogenous mediators that modulate trained immunity in the host are only partially understood, but increasing evidence supports the concept that the interleukin (IL)-1 family of cytokines plays an important role. In this review, we will highlight key findings from studies that provide insight into the multifaceted roles of members of the IL-1 family for trained immunity. Finally, we will discuss how the recent advances of our understanding on the role of IL-1 cytokines in this field may lead to new therapeutic strategies for treatment of common conditions, such as IL-1-driven autoinflammatory diseases.

IL-1 receptor regulates S100A8/A9-dependent keratinocyte resistance to bacterial invasion

Previously, we reported that epithelial cells respond to exogenous interleukin (IL)-1α by increasing expression of several genes involved in the host response to microbes, including the antimicrobial protein complex calprotectin (S100A8/A9). Given that S100A8/A9 protects epithelial cells against invading bacteria, we studied whether IL-1α augments S100A8/A9-dependent resistance to bacterial invasion of oral keratinocytes. When inoculated with Listeria monocytogenes, human buccal epithelial (TR146) cells expressed and released IL-1α. Subsequently, IL-1α-containing media from Listeria-infected cells increased S100A8/A9 gene expression in naïve TR146 cells an IL-1 receptor (IL-1R)-dependent manner. Incubation with exogenous IL-1α decreased Listeria invasion into TR146 cells, whereas invasion increased with IL-1R antagonist. Conversely, when S100A8/A9 genes were knocked down using short hairpin RNA (shRNA), TR146 cells responded to exogenous IL-1α with increased intracellular bacteria. These data strongly suggest that infected epithelial cells release IL-1α to signal neighboring keratinocytes in a paracrine manner, promoting S100A8/A9-dependent resistance to invasive L. monocytogenes.

Effect of Traumeel S on cytokine profile in a cecal ligation and puncture (CLP) sepsis model in rats

BACKGROUND

Sepsis results in significant morbidity and mortality, with current treatment options limited with respect to efficacy as well as safety. The complex homeopathic remedy Traumeel S has been shown to have both anti-inflammatory and immunostimulatory effects in the in vitro setting.

OBJECTIVES

The objective was to explore the effects of Traumeel S in an in vivo setting, using a cecal ligation and puncture (CLP) sepsis model in rats, evaluating the effects of the medication on cytokine activity.

DESIGN

Sepsis was induced in 30 rats using accepted CLP methodology. Following the procedure, rats were randomly allocated to receive an intraperitoneal injection of either Traumeel S (n=15) or normal saline (n=15). At 6 hours post-CLP, serum cytokines (interleukin [IL]-1β, tumor necrosis factor-α, IL-6, and IL-10) were evaluated.

RESULTS

IL-1β levels were significantly higher in the treatment group (p=0.03) with no significant differences found between the groups with respect to the other cytokines tested.

CONCLUSIONS

In contrast to in vitro studies, Traumeel significantly increased IL-1β levels in an in vivo model, without influencing other cytokines. IL-1β is a proinflammatory cytokine that has been shown to have a protective effect in the CLP rat model. Further research is warranted to examine this finding, as well as its clinical implications.

Detrimental role of endogenous nitric oxide in host defence against Sporothrix schenckii

We earlier demonstrated that nitric oxide (NO) is a fungicidal molecule against Sporothrix schenckii in vitro. In the present study we used mice deficient in inducible nitric oxide synthase (iNOS-/-) and C57BL/6 wild-type (WT) mice treated with Nomega-nitro-arginine (Nitro-Arg-treated mice), an NOS inhibitor, both defective in the production of reactive nitrogen intermediates, to investigate the role of endogenous NO during systemic sporotrichosis. When inoculated with yeast cells of S. schenckii, WT mice presented T-cell suppression and high tissue fungal dissemination, succumbing to infection. Furthermore, susceptibility of mice seems to be related to apoptosis and high interleukin-10 and tumour necrosis factor-alpha production by spleen cells. In addition, fungicidal activity and NO production by interferon-gamma (IFN-gamma) and lipopolysaccharide-activated macrophages from WT mice were abolished after fungal infection. Strikingly, iNOS-/- and Nitro-Arg-treated mice presented fungal resistance, controlling fungal load in tissues and restoring T-cell activity, as well as producing high amounts of IFN-gamma Interestingly, macrophages from these groups of mice presented fungicidal activity after in vitro stimulation with higher doses of IFN-gamma. Herein, these results suggest that although NO was an essential mediator to the in vitro killing of S. schenckii by macrophages, the activation of NO system in vivo contributes to the immunosuppression and cytokine balance during early phases of infection with S. schenckii.

Lactoferrin accelerates reconstitution of the humoral and cellular immune response during chemotherapy-induced immunosuppression and bone marrow transplant in mice

Experimental evidence from previous studies supports the conclusion that orally administered lactoferrin (LF) restores the immune response in mice treated with a sublethal dose of cyclophosphamide (CP). The aim of this study was to elucidate potential benefit of LF in mice undergoing chemotherapy with busulfan (BU) and CP, followed by intravenous (i.v.) injection of bone marrow cells. CBA mice were treated orally with busulfan (4 mg/kg) for 4 consecutive days, followed by two daily doses of CP delivered intraperitoneally (i.p.) at a dose of 100 mg/kg and reconstituted next day with i.v. injection of 10(7) syngeneic bone marrow cells. One group of these mice was given LF in drinking water (0.5% solution). After treatment, mice were immunized with ovalbumin (OVA) to subsequently measure delayed type hypersensitivity responsiveness and with sheep red blood cells to determine humoral immunity by evaluation of splenic antibody-forming cells. As expected, both humoral and cellular immune responses of mice that were treated with these chemotherapeutic agents was markedly impaired. Here we report that this impairment was remarkably attenuated by oral administration of LF. Humoral immunity fell to levels that were 66-88% lower than that of untreated animals. Humoral immunity of LF-treated animals was equivalent to that of untreated mice within 1 month. Cellular immune responses were inhibited by chemotherapy treatment to a lesser degree, reaching levels that were approximately 50% lower than those of untreated animals. Again, LF mitigated this decrease, resulting in responses that were only slightly lower than those observed in untreated animals. Furthermore, when mice were given a lethal dose of BU (4 x 25 mg daily doses, i.p.) followed by a bone marrow transplant, LF caused enhanced lympho-, erythro-, and myelopoiesis in the bone marrow and appearance of transforming splenic lymphoblasts, similar to effects caused by administration of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF). In summary, our study suggests that LF may be a useful agent to accelerate restoration of immune responsiveness induced by chemotherapy in bone marrow transplant recipients.

Enhanced clearance of Escherichia coli and Staphylococcus aureus in mice treated with cyclophosphamide and lactoferrin

Previous studies on cyclophosphamide (CP)-immunocompromised mice showed accelerated reconstitution of immune system function following oral treatment with lactoferrin (LF). The aim of this investigation was to evaluate the ability of mice, treated with a sublethal dose of CP and given LF, to combat bacterial infections. Mice were injected with a single, intraperitoneal dose of CP (350 mg/kg body weight). One group of CP-treated mice was also given LF in drinking water (0.5% solution) for 14 days. Untreated and LF-treated mice served as controls. On day 15 following CP administration, mice were infected intravenously with 10(8) Escherichia coli or 5 x 10(7) Staphylococcus aureus. Twenty-four hours later, the number of colony-forming units (CFU) in spleens and livers were determined. Phenotypic analysis of blood leukocytes was determined, as well as the ability of splenic and peritoneal cells to produce IL-6 spontaneously and in the presence of lipopolysaccharide (LPS). Treatment with CP, or with CP and LF, led to profound reduction of E. coli CFU in the liver and the spleen; treatment with LF alone had significant inhibitory effects on organ enumerated CFU. S. aureus CFUs were also significantly reduced in spleens of mice treated with CP or CP/LF and, to a lesser degree, after LF alone. These effects were also significantly reduced in the livers. Analysis of blood cellular phenotype revealed total number of peripheral leukocytes was lower in the CP-treated group (52.6%) but not significantly different from control values in CP/LF and LF-treated groups (90.7% and 104.6%, respectively). Conversely, percentage of blood neutrophils was markedly elevated in CP and CP/LF groups--62% and 42.5% vs. 18.4% in controls. These findings were accompanied by production of IL-6 by splenic and peritoneal cells which was significantly increased in CP- and CP/LF-treated groups. It was concluded that the increased clearance of bacteria in the organs of mice treated with CP and CP/LF may result from a rise in the number of neutrophils infiltrating the organs and contributing to accelerated clearance of bacteria. The study also suggests that the ability of cells from CP- and CP/LF-treated mice to produce significantly more IL-6 may also contribute to increased resistance to infections. Lastly, together with our previous data, this study indicates that LF used to reconstitute the antigen-specific immune response in CP-treated mice does not impair their resistance to infection.

Augmentation of T cell levels and responses induced by androgen deprivation

Androgen has been implicated as a negative regulator of host immune function and a factor contributing to the gender dimorphism of autoimmunity. Conversely, androgen deprivation has been suggested to potentiate male host immunity. Studies have shown that removal of androgen in postpubertal male mice produces an increase in size and cellularity of primary and peripheral lymphoid organs, and enhances a variety of immune responses. Yet, few details are known about the effect of androgen removal on T cell-mediated immunity. In this study, we demonstrate two pronounced and independent alterations in T cell immunity that occur in response to androgen deprivation, provided by castration, in postpubertal male mice. First, we show that levels of T cells in peripheral lymphoid tissues of mice are increased by androgen deprivation. Second, T cells from these mice transiently proliferate more vigorously to TCR- and CD28-mediated costimulation as well as to Ag-specific activation. In addition, androgen deprivation accelerates normalization of host T and B cell levels following chemotherapy-induced lymphocyte depletion. Such alterations induced by androgen deprivation may have implications for enhancing immune responses to immunotherapy and for accelerating the recovery of the immune system following chemotherapy.

Reconstitution of the cellular immune response by lactoferrin in cyclophosphamide-treated mice is correlated with renewal of T cell compartment

Cyclophosphamide is an alkylating agent used to treat both malignant and non-malignant immune-mediated inflammatory disorders in humans. It is also known as a potent immunosuppressive drug in humans and experimental animals. The aim of this study was to evaluate the effects of oral administration of lactoferrin (LF) on cellular responses and reconstruction of the lymphocyte pool in mice treated with cyclophosphamide (CP). Twelve week-old CBA mice were given a single intraperitoneal (i.p.) dose of CP (400 mg/kg body weight), then were treated per os with seven doses of LF (1 mg/dose) on alternate days. We demonstrated that the magnitude of delayed type hypersensitivity to ovalbumin, strongly diminished by CP action, was reconstituted by LF. Oral LF treatment also resulted in partial recovery of Concanavalin A-induced splenocyte proliferation. Blood profile analysis revealed elevation of leukocytosis by LF in CP-treated mice (from 64.9 to 84.76% of the control value). LF also caused substantial restoration of the percentage of the lymphocyte population in circulating blood (from 43.4 to 60.2% of the control values). LF alone had no effect on the neutrophil/lymphocyte ratio in normal mice, however, the total number of leukocytes decreased by 23.25%. Furthermore, we showed that LF increased the cellularity of spleens isolated from CP-treated mice (from 53.2 to 78.8%) and the content of peritoneal and alveolar macrophages (elevations from 50.6 to 67.3% and from 65.2 to 83.6%, respectively). Lastly, using panning technique, we demonstrated that LF strongly elevated the pool of CD3+ T cells in normal and CP-immunocompromised mice and CD4+ T cell content. In conclusion, we showed for the first time that lactoferrin, given orally to CP-immunosuppressed mice, could reconstitute a T-cell mediated immune response by renewal of the T cell pool.

Proinflammatory Cytokines in the Treatment of Bacterial and Fungal Infections

Mortality due to severe bacterial infections has not been markedly effected by the introduction of new antimicrobial drugs over the last 30-40 years. This has emphasized the need for development of new therapeutic strategies to combat sepsis. The outcome of an infection depends on two factors: the growth of the microorganisms (including the effect of antibacterial drugs), and the host's defensive response to the invading organism. It is known that injection of bacterial products into experimental animals leads to enhanced nonspecific resistance to a variety of microorganisms. The discovery of the specific mediators responsible for modulation of host defense has created new possibilities for the development of alternative treatment strategies. Molecules such as interleukins, interferons, tumor necrosis factors and hematopoietic growth factors have become available in recombinant form, and their therapeutic potential in various infectious diseases has been tested in various experimental models of infections. Initial data in various patient groups indicate that adjunctive therapy with recombinant proinflammatory cytokines may have beneficial effects in the treatment of bacterial and fungal infections.

Reduced tissue macrophage population in the lung by anticancer agent cyclophosphamide: restoration by local granulocyte macrophage-colony-stimulating factor gene transfer

Granulocytopenia is thought to be the sole mechanism underlying the increased susceptibility to bacterial infection in hosts with anticancer chemotherapy. Little is known about the functional state of tissue macrophage populations in such hosts. Using a model of chemotherapy-induced leukopenia, the number and function of alveolar macrophages (AMS) were examined during and after multiple injections of an anticancer agent, cyclophosphamide (CP). Although CP quickly reduced peripheral blood leukocytes, the number of these cells rebounded quickly 3 to 4 days after the withdrawal of CP. Accompanying blood leukopenia was a profound reduction in the number of AMs. Contrary to the rapid onset of blood leukopenia, tissue macrophage deficiency was a more chronic process that worsened gradually as the CP regimen continued. Of importance, in contrast to blood leukopenia, which restored itself shortly after CP withdrawal, tissue macrophage deficiency was not immediately self-recoverable in spite of a restored number of circulating leukocytes. Although AMS had a decreased ability to proliferate during, but not after, the CP regimen, these cells retained a normal ability to release tumor necrosis factor-alpha and nitric oxide. To identify the potential therapeutics for recovering macrophages, a gene vector expressing granulocyte macrophage-colony-stimulating factor (GM-CSF) was delivered either systemically or locally. GM-CSF transgene was able to expand macrophage populations only when delivered to the lung after, but not during, the CP regimen. This study thus identifies tissue macrophage deficiency as a mechanism of weakened innate immunity by chemotherapy and suggests the usefulness of topical GM-CSF transgene expression for restoring innate immunity in the lung.

G551D cystic fibrosis mice exhibit abnormal regulation of inflammation in lungs and macrophages

The major cause of death in cystic fibrosis (CF) is chronic lung disease associated with persistent infection by the bacterium, Pseudomonas aeruginosa. S100A8, an S-100 calcium-binding protein with chemotactic activity, is constitutively expressed in the lungs and serum of CF patients. Levels of S100A8 mRNA were found to be three to four times higher in the lungs of mice carrying the G551D mutation in CF transmembrane conductance regulator compared with littermate controls. Intravenous injection of bacterial LPS induced S100A8 mRNA in the lung to a greater extent in G551D mice than in wild-type littermates. Localization of S100A8 mRNA and protein in the lung indicate that it is a marker for neutrophil accumulation. Bone marrow-derived macrophages from G551D mice were shown to also exhibit hypersensitivity to LPS, measured by induction of TNF-alpha. These results provide evidence that the pathology of CF relates to abnormal regulation of the immune system.

Inhibition by leukotriene inhibitors, and calcium and platelet-activating factor antagonists, of acute gastric and intestinal damage in arthritic rats and in cholinomimetic-treated mice

The leukotrienes, platelet activating factor and intracellular calcium have been implicated in the development of gastro-intestinal lesions induced by non-steroidal anti-inflammatory drugs (NSAIDs) but the relative significance of these inflammatory mediators in lesion formation has not been established in sensitive and specific models of gastro-intestinal ulceration. In the present study the effects of drugs affecting 5-lipoxygenase activity, the actions of platelet activating factor and intracellular calcium on the development of gastric and intestinal ulceration induced by NSAIDs were investigated in highly sensitive models of ulcerogenicity induced by treatment with either the cholinomimetic, acetyl-beta-methyl choline chloride, in mice (gastric mucosal lesions) or adjuvant-induced polyarthritis in rats (gastric and intestinal mucosal lesions) as well as in normal mice (intestinal mucosal lesions). The 5-lipoxygenase inhibitors, such as MK-886 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2-+ ++dimethylpropanoic acid), given at doses shown to reduce the indomethacin-induced increase in mucosal leukotriene B4 concentrations were found to partially prevent the development of gastric and intestinal lesion induced by indomethacin and gastric lesions from aspirin, but the same doses of MK-886 did not affect gastric lesions from diclofenac. Pretreatment with these inhibitors at both 3-5 h and 0-0.25 h was required to achieve protection against gastric mucosal damage from indomethacin. Immediate prior administration of platelet activating factor antagonists (e.g. WEB-2086) with the 5-lipoxygenase inhibitors did not affect gastric or intestinal lesions induced by indomethacin. The calcium antagonist, verapamil, was slightly protective against gastric and intestinal lesions induced by indomethacin. Gastric lesions were further prevented by combinations of a single dose of verapamil with a platelet activating factor antagonist but not combined with a 5-lipoxygenase inhibitor; other combinations of verapamil with lipoxygenase inhibitors or platelet-activating factor antagonists being without inhibitory effects on gastric or intestinal lesions compared with the drugs alone. These results show that 5-lipoxygenase products and intracellular calcium play a major role in acute gastric and intestinal damage by the NSAIDs, but platelet-activating factor has little or no appreciable involvement.

Proinflammatory cytokines and treatment of disease

Bacterial infections in the immunocompromised host cause considerable mortality, and even recently developed antimicrobial strategies often fail to cure these infections, especially in granulocytopenic patients. Cytokines and hematopoietic growth factors have been shown to stimulate host defense mechanisms in vitro and in vivo. The possible role of the proinflammatory cytokines interleukin (IL)-1, tumor necrosis factor-alpha, IL-6, and IL-8 as modulators of host resistance to bacterial infections is discussed. Interleukin-1 has been effective in various animal models of potentially lethal bacterial infection, even during severe granulocytopenia. The protective mechanism of IL-1 may be mediated by downregulation of cytokine receptors and cytokine production and induction of acute phase proteins. Moreover, in subacute and chronic infections IL-1 interferes with microbial outgrowth via mechanisms that have only been partly elucidated.

Granulocyte-macrophage colony-stimulating factor in Staphylococcus aureus-induced arthritis

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine that is able to increase not only the production of phagocytic cells but also their efficacy with respect to, e.g., bactericidal properties. In this study, we wanted to analyze the impact of GM-CSF on experimental Staphylococcus aureus-induced arthritis. For that purpose, mice were administered GM-CSF before and after bacterial inoculation. Although there was an increase in the total number of leukocytes as well as in the granulocyte fraction, there was no favorable effect on the severity of arthritis or on survival rates. There were no obvious differences between the GM-CSF-pretreated animals and controls with regard to growth of staphylococci in joints and kidneys 4 days after the bacterial inoculation. In contrast, mice that had been pretreated with GM-CSF prior to bacterial inoculation showed approximately four times lower numbers of bacteria in their blood 24 h later. These results, along with those of our previous studies, suggest that on the one hand the granulocyte is the main protective cell during the course of S. aureus infection but that on the other hand, upregulation of granulocyte-macrophage production will not exert any additional protective effects with respect to tissue injury.

Granulocyte-macrophage colony-stimulating factor in amniotic fluid and in airway specimens of newborn infants

Granulocyte-macrophage colony-stimulating factor (GM-CSF), a cytokine that promotes white cell maturation, participates in the metabolism of pulmonary surfactant. Little is known on the production of GM-CSF during pregnancy or the neonatal period. We studied how the concentrations of GM-CSF in amniotic fluid (AF) or in tracheal aspirates (TA) of newborn infants are influenced by length of gestation, postnatal age, as well as conditions affecting the mother or the fetus. One hundred and forty-three AF samples from 143 pregnant patients (gestational age range, 28-42 wk) and 202 TA samples from 82 neonates (gestational age, 24-42.5 wk, postnatal age 0.2 d to 4 wk) were analyzed for GM-CSF using ELISA. In patients with intact membranes, AF GM-CSF increased as a function of gestational age; the concentrations were below 7.5 ng/L (detection limit of the assay) (n = 5), 18.6 +/- 2.3 ng/L (n = 56), and 56.7 +/- 7.9 ng/L (n = 58) at gestational ages between 28 and 32 wk, between 32 and 37 wk, and in term patients, respectively (linear regression: r = 0.404, p = 0.001). Among patients at less than 33 wk of gestation, those with intact membranes had a median AF GM-CSF concentration under the detection limit (n = 7), whereas in those with preterm premature rupture of membranes, the concentration was 50.1 +/- 22.2 ng/L (n = 16) (p = 0.002). Among term patients, those in labor had higher AF GM-CSF than those without signs of labor. TA GM-CSF at less than 12 h of age correlated with gestational age (r = 0.654, p = 0.0002, n = 28); thereafter, TA GM-CSF increased, and gestation dependence disappeared. We conclude that GM-CSF in AF and in fetal lung liquid is developmentally regulated and GM-CSF production increases in inflammatory conditions during pregnancy.

The role of TNF-alpha in fever: opposing actions of human and murine TNF-alpha and interactions with IL-beta in the rat

1. The role of tumour necrosis factor-alpha (TNF-alpha) in fever is controversial. Some studies have indicated that TNF-alpha acts as a cryogen to inhibit fever, while others suggest that TNF-alpha is an endogenous pyrogen which mediates fever. The majority of studies in experimental animals supporting a cryogenic action have been conducted using human (h)TNF-alpha, which has been shown to bind only to one (p55) of the two TNF-alpha receptors in rodents. 2. The aim of the present investigation was to study the role of TNF-alpha in fever by comparing effects of hTNF-alpha, which binds only to the p55 receptor, with those of murine (m) TNF-alpha, which binds to both p55 and p75 TNF-alpha receptors, and to investigate the relationship between TNF-alpha and interleukin-1 (IL-1), an important endogenous pyrogen. 3. Injection of hTNF-alpha (0.3-10 micrograms kg-1, i.p.) had no effect on core temperature in conscious rats (measured by remote radiotelemetry), whereas mTNF-alpha (3 micrograms kg-1) induced fever which was maximal 1 h after the injection (38.2 +/- 0.2 degrees C compared to 37.3 +/- 0.1 degrees C in controls). Intracerebroventricular (i.c.v.) administration of either form of TNF-alpha elicited dose-dependent fever at doses higher than 0.12 microgram kg-1. 4. Peripheral injection of hIL-1 beta (1 microgram kg-1) resulted in fever (38.3 +/- 0.2 degree C compared to 37.2 +/- 0.1 degrees C in controls at 2 h), which was significantly attenuated (P < 0.01) by co-administration of a sub-pyrogenic dose of hTNF-alpha (1 microgram kg-1), but was unaffected by co-administration of mTNF-alpha (0.1 or 0.3 microgram kg-1, i.p.). In contrast, intracerebroventricular (i.c.v.) co-administration of a sub-pyrogenic dose (0.12 microgram kg-1) of hTNF-alpha did not attenuate fever induced by intraperitoneal (i.p.) injection of IL-1 beta, and sub-pyrogenic dose (0.12 microgram kg-1, i.c.v.) of mTNF-alpha significantly prolonged the febrile response to IL-1 beta. Pretreatment of animals with anti-TNF-alpha antiserum (i.c.v.) did not affect the febrile response to systemic IL-1 beta. 5. Animals injected i.p. with a pyrogenic dose of mTNF-alpha developed fever (38.2 +/- 0.2 degrees C compared to 37.3 +/- 0.1 degrees C in controls 2 h after the injection) that was completely abolished by peripheral administration of IL-1ra (2 mg kg-1, P < 0.001), while i.c.v. administration of IL-1ra (400 micrograms/rat) did not affect mTNF-alpha-induced fever. 6. These data indicate that endogenous TNF-alpha is probably a pyrogen and that previous results suggesting cryogenic actions of TNF-alpha resulted from the use of a heterologous protein in the rat. The markedly contrasting effects of mTNF-alpha and TNF-alpha could result from different interactions with the two TNF-alpha receptor subtypes. The data also suggest that fever induced by exogenous TNF-alpha is mediated via release of IL-1 beta in peripheral tissues, but not in the brain.

Immunological status of ENL (erythema nodosum leprosum) patients: its relationship to bacterial load and levels of circulating IL-2R

Recent data suggest that the clinical course of reactional states in leprosy is closely related to the cytokine profile released locally or systemically by the patients. In the present study, patients with erythema nodosum leprosum (ENL) were grouped according to the intensity of their clinical symptoms. Clinical and immunological aspects of ENL and the impact of these parameters on bacterial load were assessed in conjunction with patients' in vitro immune response to mycobacterial antigens. In 10 out of the 17 patients tested, BI (bacterial index) was reduced by at least 1 log from leprosy diagnosis to the onset of their first reactional episode (ENL), as compared to an expected 0.3 log reduction in the unreactional group for the same MDT (multidrug therapy) period. However, no difference in the rate of BI reduction was noted at the end of MDT among ENL and unreactional lepromatous patients. Accordingly, although TNF-alpha (tumor necrosis factor) levels were enhanced in the sera of 70.6% of the ENL patients tested, no relationship was noted between circulating TNF-alpha levels and the decrease in BI detected at the onset of the reactional episode. Evaluation of bacterial viability of M. leprae isolated from the reactional lesions showed no growth in the mouse footpads. Only 20% of the patients demonstrated specific immune response to M. leprae during ENL. Moreover, high levels of soluble IL-2R (interleukin-2 receptor) were present in 78% of the patients. Circulating anti-neural (anti-ceramide and anti-galactocerebroside antibodies) and anti-mycobacterial antibodies were detected in ENL patients' sera as well, which were not related to the clinical course of disease. Our data suggest that bacterial killing is enhanced during reactions. Emergence of specific immune response to M. leprae and the effective role of TNF-alpha in mediating fragmentation of bacteria still need to be clarified.

Interleukin-1 (IL-1)-induced resistance to bacterial infection: role of the type I IL-1 receptor

Pretreatment with a low dose of recombinant human interleukin-1 beta (IL-1) (3 to 30 micrograms/kg) 24 h before a lethal Pseudomonas aeruginosa infection prolongs survival in neutropenic mice. We investigated the role of the type I IL-1 receptor (IL-1RI) and IL-1RII in this IL-1-induced protection by using a specific IL-1 receptor antagonist (IL-1-Ra), which blocks effects mainly via IL-1RI. Pretreatment with IL-1Ra before IL-1 partially blocked the IL-1-induced enhanced survival, whereas pretreatment with a specific neutralizing monoclonal antibody to IL-1RI (35F5) eliminated the IL-1 induced protection. The nonapeptide fragment 163-171 of recombinant human IL-1 beta, which possesses the immunoadjuvant but not the inflammatory effect of the entire molecule via a non-receptor-mediated signal transduction process, did not reproduce the IL-1-induced protection. IL-1-induced protection was associated with reduced serum aspartate aminotransferase and alanine aminotransferase concentrations in conjunction with ameliorated histopathology of the liver. These findings may be due to reduced cytokine production and cytokine sensitivity of target cells after infection. We conclude that the IL-1-induced nonspecific resistance to infection is mediated by cells bearing IL-1RI and is associated with a reduction of liver damage.

Interleukin-1 and related pro-inflammatory cytokines in the treatment of bacterial infections in neutropenic and non-neutropenic animals

Bacterial infections in the immunocompromized host cause considerable mortality, and even the recently developed antimicrobial strategies often fail to cure these infections, especially in granulocytopenic patients. Cytokines and hematopoietic growth factors have been shown to stimulate host defense mechanisms in vitro and in vivo. We discuss the possible role of the pro-inflammatory cytokines interleukin-1, tumor necrosis factor-alpha, interleukin-6 and interleukin-8 as modulators of host resistance to bacterial infections. Interleukin-1 has been shown effective in various animal models of potentially lethal bacterial infection, even during severe granulocytopenia. The protective mechanism of interleukin-1 may be mediated via downregulation of cytokine receptors and cytokine production, and via induction of acute phase proteins. Moreover, in subacute and chronic infections interleukin-1 interferes with microbial outgrowth, via mechanisms that have only been partially elucidated.