Contribution of fucose-containing capsules in Klebsiella pneumoniae to bacterial virulence in mice

Bacterium Klebsiella pneumoniae (KP) contains a prominent capsule. Clinical infections usually are associated with pneumonia or urinary tract infection (UTI). Emerging evidence implicates KP in severe liver abscess especially in diabetic patients. The goal of this study was to investigate the capsular polysaccharides from KP of liver abscess (hepatic-KP) and of UTI-KP. The composition of capsular polysaccharides was analyzed by capillary high-performance liquid chromatography (HPLC, Dionex system). The terminal sugars were assayed by binding ability to lectins. The results showed that the capsule of a hepatic KP (KpL1) from a diabetic patient contained fucose, while the capsule from UTI-KP (KpU1) did not. The absence of fucose was verified by the absence of detectable polymerase chain reaction (PCR) fragment for fucose synthesis genes, gmd and wcaG in KpU1. Mice infected with the KpL1 showed high fatality, whereas those infected with the KpU1 showed high survival rate. The KpL1 capsule was reactive to lectins AAA and AAL, which detect fucose, while the KpU1 capsule was reactive to lectin GNA, which detects mannose. Phagocytosis experiment in mouse peritoneal cavity indicated that the peritoneal macrophages could interact with KpU1, while rare association of KpL1 with macrophages was observed. This study revealed that different polysaccharides were displayed on the bacterial capsules of virulent KpL1 as compared with the less virulent KpU1. Interaction of KpU1 with mice peritoneal macrophages was more prominent than that of KpL1. The possession of fucose might contribute to KpL1 virulence by avoiding phagocytosis since fucose on bacteria had been implicated in immune evasion.     

Pteris multifida,Cortex phellodendri,and probiotics attenuated inflammatory status and immunity in mice with a Salmonella enterica serovar Typhimurium infection

Pteris multifida (PM) and Cortex phellodendri (CP) are medicinal foods used for gastrointestinal protection. Lactic-acid bacteria are probiotics. Salmonella Typhimurium strain ST21-infected mice were used to examine the alleviative effects of two lactic-acid bacteria (LAB) as well as aqueous extracts of PM and CP for a 4-day treatment. CP and LAB decreased fecal ST counts. CP and PM reduced the ST21 count in the blood, intestine, and liver. LAB lowered the ST21 count in the intestine and spleen. CP and LAB decreased the IFN-gamma level; PM lowered the TNF-alpha level; and both LAB and PM reduced the IL-1beta level in serum. PM and CP lowered the IgG level in serum. The data in a macrophage infection model indicate that TNF-alpha was partial involved in this alleviative effects, other mechanisms might be involved. In sum, these novel findings suggest that PM, CP, and LAB probiotics are potential anti-Salmonellae agents.     

Damping excessive inflammation and tissue damage in Mycobacterium tuberculosis infection by Toll IL-1 receptor 8/single Ig IL-1-related receptor, a negative regulator of IL-1/TLR signaling

Toll IL-1R 8/single Ig IL-1-related receptor (TIR8/SIGIRR) is a member of the IL-1R family, expressed by epithelial tissues and immature dendritic cells, and is regarded as a negative regulator of TLR/IL-1R signaling. Tir8-deficient mice were rapidly killed by intranasal administration of low doses of Mycobacterium tuberculosis, despite controlling efficiently the number of viable bacilli in different organs. Tir8(-/-)-infected mice showed an increased number of neutrophils and macrophages in the lungs; however, mycobacteria-specific CD4 and CD8 T cells were similar in Tir8(-/-) and Tir8(+/+) mice. Exaggerated mortality of Tir8(-/-) mice was due to massive liver necrosis and was accompanied by increased levels of IL-1beta and TNF-alpha in lung mononuclear cells and serum, as well as by increased production of IL-1beta and TNF-alpha by M. tuberculosis-infected dendritic cells in vitro. Accordingly, blocking IL-1beta and TNF-alpha with a mix of anti-cytokine Abs, significantly prolonged survival of Tir8(-/-) mice. Thus, TIR8/SIGIRR plays a key role in damping inflammation and tissue damage in M. tuberculosis infection.     

Mitogen-activated protein kinase (MAPK) signalling pathways in HepG2 cells infected with a virulent strain of Klebsiella pneumoniae

Klebsiella pneumoniae (KP), an enterobacterium, usually causes urinary tract infection or pneumonia; however, it has caused severe liver abscess in diabetic patients in recent years. How this emerging virulent KP strain causes liver abscess is not known. This study investigates signalling pathways in HepG2 cells infected by virulent KP. Cells were infected with bacteria for various durations and harvested to screen for signalling molecules by Western blotting. Our results showed that phosphorylated mitogen-activated protein kinase (MAPK) kinase (MEK) 1/2, p44/p42 MAPK and p90 ribosomal S6 kinase (p90RSK) were observed and this pathway was inhibited by MEK1/2 inhibitors U0126 and PD98059. Phosphorylation of MEK3/6, p38 kinase and ATF-2 was also observed and this pathway was inhibited by p38 kinase inhibitors SB203850 and SB202190. Toll-like receptor (TLR) 2 and 4 expressions were increased and maximized 2-4 h post infection. The JNK pathway, Elk, MAPKAPK-2 and HSP27 were not activated. These results suggest that KP infections induce signal transduction through TLR2 and TLR4 and activate two downstream MAP kinase pathways, MEK1/2-p44/p42 MAPK-p90RSK and MEK3/6-p38 kinase-ATF-2, but not the JNK pathway in HepG2 cells. The infected HepG2 eventually showed apoptosis and died.     

Modification of susceptibility to Klebsiella pneumoniae during murine cytomegalovirus infection

The effect of murine cytomegalovirus (MCMV) infection on susceptibility to bacterial infection was studied in mice by a combination of intraperitoneal (ip) inoculation of a sublethal dose of MCMV with subsequent ip challenge of 2 X 10(3) cfu of a strain of Klebsiella pneumoniae (KP). When given alone, KP produced a mortality of 30-40%. Mortality was increased when KP was given 1 to 7 days after MCMV injection with the peak increase at the 4th to 5th day when 100% mortality occurred. Virus levels in various organs of mice infected with MCMV alone, or superinfected with KP did not differ. Bacterial counts on the other hand, showed that increased mortality in mixed MCMV and KP infected mice was due to an uncontrolled growth of bacteria at the site of primary lodgment, i.e., the peritoneum, and severe systemic infection. Neutrophil response to growth of KP during the first 3 days of bacterial infection was defective in MCMV infected mice. While the initial clearance of KP from the blood was more efficient in MCMV infected mice, probably due to activated reticuloendothelial function, it did not protect the mice against KP infection. Using the in vivo model, it was shown that poor neutrophil response and possibly other defective neutrophil functions were responsible for increased mortality to KP infection in MCMV infected mice.     

Balance of tumor necrosis factor alpha and interleukin-10 in a buccal infection in a streptozotocin-induced diabetic rat model

This study evaluates the local levels of proinflammatory cytokine, tumor necrosis factor alpha (TNF-alpha), and anti-inflammatory cytokine, interleukin-10 (IL-10), in an experimental buccal abscess of a diabetic rat model. We prepared a buccal cavity induced by injection of carrageenin in a diabetic rat (blood glucose, 460.6 +/- 54.7 mg/dl, mean +/- SE) induced by streptozotocin (STZ). The buccal abscess was formed by the direct inoculation of Streptococcus pyogenes S-8 (2 x 10(7) cfu) into the buccal cavity at day 5 after carrageenin injection. Cytokine levels in the exudate of the buccal abscess were measured by enzyme-linked immunosorbent assay for 48 h after infection. Bacterial counts, weighing of exudate, and histological analysis were also performed. The mean TNF-alpha levels in the buccal abscess exudate of the diabetic group, which were generally higher than those of the control group, tended to increase over time until 48 h after infection, while the TNF-alpha levels in the control group peaked at 24 h after infection and then decreased. The IL-10 levels in the diabetic group remained almost unchanged until 48 h after infection, while the IL-10 levels in the control group were significantly higher than in the diabetic group at 12-24 h after infection. The mean ratio of TNF-alpha to IL-10 levels was 1.17-1.67 in the diabetic group, which was higher than the 0.26-0.69 of the control group. The bacterial counts in the buccal abscess and the weight of exudate were significantly higher in the diabetic group compared to the control group at 36-48 h. Histological findings showed that inflammatory cell infiltration was remarkable in the diabetic group compared to that of the control group. These results suggest that the elevated proinflammatory TNF-alpha levels and decreased anti-inflammatory IL-10 levels, which are produced at local infection sites, may at least in part be related to the severity of inflammation in this rat model with diabetes induced by STZ.     

Virulent aggregates of Streptococcus pyogenes are generated by homophilic protein-protein interactions

Many strains of the important human pathogen Streptococcus pyogenes form aggregates when grown in vitro in liquid medium. The present studies demonstrate that this property is crucial for the adherence, the resistance to phagocytosis and the virulence of S. pyogenes. A conserved sequence of 19 amino acid residues (designated AHP) was identified in surface proteins of common S. pyogenes serotypes. This sequence was found to promote bacterial aggregation through homophilic protein-protein interactions between AHP-containing surface proteins of neighbouring bacteria. A synthetic AHP peptide inhibited S. pyogenes aggregation, reduced the survival of S. pyogenes in human blood and attenuated its virulence in mice. In contrast, mutant bacteria devoid of surface proteins containing AHP-related sequences did not aggregate or adhere to epithelial cells. These bacteria are also rapidly killed in human blood and show reduced virulence in mice, underlining the pathogenic significance of the AHP sequence and S. pyogenes aggregation.     

Shedding of TNF-alpha receptors, blood pressure, and insulin sensitivity in type 2 diabetes mellitus

Tumor necrosis factor-alpha (TNF-alpha) is increasingly recognized as a key component in the development of insulin resistance and increased blood pressure. In a sample of 368 individuals, the ratio of soluble TNF-alpha receptors (sTNFR2/sTNFR1) correlated positively with systolic and diastolic blood pressure (P < 0.01). This ratio was significantly greater in type 2 diabetic subjects (DM-2) than in type 1 diabetic patients and was greater than in control nondiabetic subjects (P < 0.00001). The TNF-alpha receptor 1 (TNFR1) density in peripheral blood monocytes was similar in DM-2 patients and in nondiabetic subjects. After phorbol 12-myristate 13-acetate, TNFR1 shedding was significantly decreased in DM-2 compared with control subjects, and it was directly associated with insulin sensitivity (r = 0.54, P = 0.03). Serum sTNFR1 concentration was also linked to the vasodilatory response to glyceryltrinitrate (P = 0.01). Conversely, TNF-alpha receptor 2 shedding was negatively associated with insulin sensitivity (r = -0.54, P = 0.03), whereas shedding of L-selectin showed no significant association. After exercise-induced lowering of blood pressure, a parallel decrease in sTNFR2/sTNFR1 was observed in DM-2 patients. Our findings suggest that insulin resistance and blood pressure are linked to altered shedding of TNF-alpha receptors in DM-2. The latter seems reversible and is not genetically determined.     

Salmonella typhimurium strains carrying independent mutations display similar virulence phenotypes yet are controlled by distinct host defense mechanisms

The outcome of Salmonella infection in the mammalian host favors whoever succeeds best in disturbing the equilibrium between coordinate expression of bacterial (virulence) genes and host defense mechanisms. Intracellular persistence in host cells is critical for pathogenesis and disease, because Salmonella typhimurium strains defective in this property are avirulent. We examined whether similar host defense mechanisms are required for growth control of two S. typhimurium mutant strains. Salmonella pathogenicity island 2 (SPI2) and virulence plasmid-cured Salmonella mutants display similar virulence phenotypes in immunocompetent mice, yet their gene loci participate in independent virulence strategies. We determined the role of TNF-alpha and IFN-gamma as well as different T cell populations in infection with these Salmonella strains. After systemic infection, IFN-gamma was essential for growth restriction of plasmid-cured S. typhimurium, while SPI2 mutant infections were controlled in the absence of IFN-gamma. TNFRp55-deficiency restored systemic virulence to both Salmonella mutants. After oral inoculation, control of plasmid-cured bacteria substantially relied on both IFN-gamma and TNF-alpha signaling while control of SPI2 mutants did not. However, for both mutants, ultimate clearance of bacteria from infected mice depended on alphabeta T cells.     

Experimental study on the possibility of treatment of some hemorrhagic fevers

After intracerebral challenge with 100 PFU of Lassa virus (strain Josiah), all infected mice (CBA/calac) died (control group). Production of pro-inflammatory cytokines (IL-1beta, TNF-alpha) significantly increased in the blood of these mice during the infection. For neutralization of increasing concentrations of these cytokines recombinant IL-1RA was used intraperitonealy at a dose 100 microg kg(-1), everyday, within 5 days from the third day after the challenge. Injections of IL-1RA decreased the concentration of IL-1beta and TNF-alpha and resulted in survival of all infected mice (treatment group). Marburg fever (strain Popp) caused in guinea pigs by 5 LD(50) of virus lead to the significant increase of TNF-alpha in the animal's blood and caused a lethal outcome (control group). Treatment of infected guinea pigs by IL-1RA or anti-TNF serum decreased the concentration of TNF-alpha and resulted in survival of half of the animals (treatment group). For the treatment recombinant IL-1RA was used at a dose 100 microg kg(-1), intramuscularly, everyday, within 6 days from the third day after the challenge or anti-TNF serum, intramuscularly 0.5 ml (2000 U ml(-1); 1 U of the antiserum neutralises 0.03 ng of TNF-alpha), everyday, within 6 days from the third day after the challenge.     

Multiple roles for tumor necrosis factor-alpha and lymphotoxin alpha/beta in immunity and autoimmunity

Tumor necrosis factor (TNF)-alpha and lymphotoxin (LT) alpha/beta play multiple roles in the development and function of the immune system. This article focuses on three important aspects of the effects of these cytokines on the immune response and on autoimmunity. In several experimental systems (Jurkat T cells, murine T-cell hybridomas), TNF-alpha appears to cause a downregulation of signaling through the TCR, revealed by changes in calcium flux, activation of p21, p23 and ZAP70, and a decrease in nuclear activation of NF-kappaB. Previous and present results suggest that TNF-alpha interferes in some manner with signaling through the TCR, at a locus yet to be delineated. Transgenic expression of LTbetaR-Fc in nonobese diabetic (NOD) transgenic mice results in prevention of type 1 diabetes in NOD mice as long as the level of expression of the fusion protein (under the control of the cytomegalovirus promoter) remains above a level of 2-3 microg/ml. Once the expression levels of the fusion protein have dropped below this critical level, the diabetic process resumes and the animals become diabetic at 40-50 weeks of age, whereas nontransgenic littermates develop diabetes by 25-30 weeks of age. The paradoxical effects of neonatal TNF-alpha administration in NOD mice in increasing incidence of and hastening onset of type 1 diabetes, while neonatal anti-TNF administration completely prevents all signs of islet cell autoimmunity, are due partly to the low levels of CD4+CD25+ T cells in NOD mice. These low levels are reduced by a further 50% on neonatal administration of nontoxic levels of TNF-alpha. In contrast, neonatal administration of anti-TNF-alpha results in a dramatic increase in the levels of CD4+CD25+ regulatory T cells, to levels beyond those seen in wild-type untreated NOD mice. TNF-alpha and LTalpha/beta thus have pleomorphic regulatory effects on the development and expression of autoimmunity.     

AGE/RAGE produces endothelial dysfunction in coronary arterioles in type 2 diabetic mice

We hypothesized that impaired nitric oxide (NO)-dependent dilation (endothelial dysfunction) in type 2 diabetes results, in part, from elevated production of superoxide (O(2)(*-)) induced by the interaction of advanced glycation end products (AGE)/receptor for AGE (RAGE) and TNF-alpha signaling. We assessed the role of AGE/RAGE and TNF-alpha signaling in endothelial dysfunction in type 2 diabetic (Lepr(db)) mice by evaluation of endothelial function in isolated coronary resistance vessels of normal control (nondiabetic, m Lepr(db)) and diabetic mice. Although dilation of vessels to the endothelium-independent vasodilator sodium nitroprusside (SNP) was not different between diabetic and control mice, dilation to the endothelium-dependent agonist acetylcholine (ACh) was reduced in diabetic vs. control mice. The activation of RAGE with RAGE agonist S100b eliminated SNP-potentiated dilation to ACh in Lepr(db) mice. Administration of a soluble form of RAGE (sRAGE) partially restored dilation in diabetic mice but did not affect dilation in control mice. The expression of RAGE in coronary arterioles was markedly increased in diabetic vs. control mice. We also observed in diabetic mice that augmented RAGE signaling augmented expression of TNF-alpha, because this increase was attenuated by sRAGE or NF-kappaB inhibitor MG132. Protein and mRNA expression of NAD(P)H oxidase subunits including NOX-2, p22(phox), and p40(phox) increased in diabetic compared with control mice. sRAGE significantly inhibited the expression of NAD(P)H oxidase in diabetic mice. These results indicate that AGE/RAGE signaling plays a pivotal role in regulating the production/expression of TNF-alpha, oxidative stress, and endothelial dysfunction in type 2 diabetes.     

MyD88-dependent signals are essential for the host immune response in experimental brain abscess

Brain abscesses form in response to a parenchymal infection by pyogenic bacteria, with Staphylococcus aureus representing a common etiologic agent of human disease. Numerous receptors that participate in immune responses to bacteria, including the majority of TLRs, the IL-1R, and the IL-18R, use a common adaptor molecule, MyD88, for transducing activation signals leading to proinflammatory mediator expression and immune effector functions. To delineate the importance of MyD88-dependent signals in brain abscesses, we compared disease pathogenesis using MyD88 knockout (KO) and wild-type (WT) mice. Mortality rates were significantly higher in MyD88 KO mice, which correlated with a significant reduction in the expression of several proinflammatory mediators, including but not limited to IL-1beta, TNF-alpha, and MIP-2/CXCL2. These changes were associated with a significant reduction in neutrophil and macrophage recruitment into brain abscesses of MyD88 KO animals. In addition, microglia, macrophages, and neutrophils isolated from the brain abscesses of MyD88 KO mice produced significantly less TNF-alpha, IL-6, MIP-1alpha/CCL3, and IFN-gamma-induced protein 10/CXCL10 compared with WT cells. The lack of MyD88-dependent signals had a dramatic effect on the extent of tissue injury, with significantly larger brain abscesses typified by exaggerated edema and necrosis in MyD88 KO animals. Interestingly, despite these striking changes in MyD88 KO mice, bacterial burdens did not significantly differ between the two strains at the early time points examined. Collectively, these findings indicate that MyD88 plays an essential role in establishing a protective CNS host response during the early stages of brain abscess development, whereas MyD88-independent pathway(s) are responsible for pathogen containment.     

Paradoxical synergistic effects of tumour necrosis factor and interleukin 1 in murine gut-derived sepsis with Pseudomonas aeruginosa.

The authors evaluated the synergistic effect of tumour necrosis factor (TNF) and interleukin 1 (IL-1) in gut-derived sepsis in mice. After colonization of Pseudomonas aeruginosa strain D4 in the gastrointestinal tract, cyclophosphamide was administered to induce bacterial translocation of the P. aeruginosa and thereby to cause gut-derived sepsis. In this model, treatment either with 8 microg/kg of recombinant human TNF-alpha (rhTNF-alpha) or 2 microg/kg of recombinant human interleukin 1alpha (rhIL-1alpha) solely did not affect the mortality, whereas combined administration of the same doses of rhTNF-alpha and rhIL-1alpha significantly increased the mortality rate in comparison with saline-treated mice. Bacterial counts in liver and blood were significantly higher in rhTNF-alpha and rhIL-1alpha treated mice than in saline-treated mice. Endogenous TNF-alpha and IL-1beta productions were stimulated after combined treatment with rhTNF-alpha and rhIL-1alpha. On the contrary to these adverse effects, combined treatment with 500 microg/kg of rhTNF-alpha and 50 microg/kg of rhIL-1alpha on the day before the administration of cyclophosphamide significantly reduced the mortality from septic infection. We conclude that TNF and IL-1 synergistically affect the mortality of mice after gut-derived sepsis due to P. aeruginosa in mice and the timing of treatment with these cytokines causes both extremes in their effects.     

Growth Hormone (GH) Hypersecretion and GH Receptor Resistance in Streptozotocin Diabetic Mice in Response to a GH Secretagogue

The growth hormone (GH) and insulin-like growth factor I (IGF-I) axis were studied in streptozotocin (STZ) diabetic and nondiabetic female mice following intravenous (IV) injection of the GH secretagogue (GHS) ipamorelin or saline. On day 14, blood samples were obtained before and 10 minutes after the injection. Livers were removed and frozen for determination of the mRNA expressions of the GH receptor, GH-binding protein, and IGF-I, and hepatic IGF-I peptide. Serum samples were analyzed for GH and IGF-I. Following ipamorelin injection, the GH levels were found to be 150 ± 35 μg/L and 62 ± 11 μg/L in the diabetic compared to the nondiabetic mice (P < .05). Serum IGF-I levels were lower in diabetic than in nondiabetic animals, and rose after stimulation only in the nondiabetic animals. Furthermore, hepatic GH resistance and IGF-I mRNA levels and IGF-I peptide were increased in nondiabetic animals in response to GH stimulation, whereas the low levels per se of all these parameters in diabetic mice were unaffected. The study shows that STZ diabetic mice demonstrate a substantial part of the clinical features of type 1 diabetes in humans, including GH hypersecretion and GH resistance. Accordingly, it is proposed that STZ diabetic mice may be a better model of the perturbations of the GH/IGF-I axis in diabetes than STZ diabetic rats.     

Roles of endogenous cytokines in liver apoptosis of mice in lethal Listeria monocytogenes infection

Various bacterial pathogens have been identified as mediators of apoptosis. Apoptosis reportedly shows both detrimental and beneficial effects on biological functions. We studied the role of liver apoptosis in lethal Listeria monocytogenes infection and the regulation of apoptosis by endogenous cytokines during infection. Apoptosis was observed in the spleen but not in the liver of infected mice, whereas the induction of liver necrosis was evident by rising levels of serum aminotransferases in these animals. Apoptosis was detected in the liver of L. monocytogenes-infected mice which had been treated with monoclonal antibody (mAb) against tumor necrosis factor-alpha (TNF-alpha) or interleukin-6 (IL-6), or in TNF-alpha(-/-) mice, but not in gamma- interferon (IFN-gamma)(-/-) mice or mice which had been treated with mAb against IL-4 or IL-10. Augmentation of liver apoptosis in mice treated with mAb against TNF-alpha or IL-6 or in TNF-alpha(-/-) mice correlated with the increase in bacterial numbers in the organ, while no augmentation of apoptosis was observed in the liver of IFN-gamma(-/-) mice irrespective of the marked increase in bacterial numbers in the organs, indicating that augmentation of liver apoptosis may not be merely due to the increase in bacterial growth in the organs. These results suggest that TNF-alpha and IL-6 may play an important role in protecting the liver from apoptosis in lethal L. monocytogenes infection.     

Yersinia enterocolitica evasion of the host innate immune response by V antigen-induced IL-10 production of macrophages is abrogated in IL-10-deficient mice.

The virulence-associated V Ag (LcrV) of pathogenic Yersinia species is part of the translocation apparatus, required to deliver antihost effector proteins (Yersinia outer proteins) into host cells. An orthologous protein (denoted as PcrV) has also been identified in the ExoS regulon of Pseudomonas aeruginosa. Additionally, it is known that LcrV is released by yersiniae into the environment and that LcrV causes an immunosuppressive effect when injected into mice. In this study, we demonstrate for the first time that rLcrV, but not PcrV, is capable of suppressing TNF-alpha production in zymosan A-stimulated mouse macrophages and the human monocytic Mono-Mac-6 cell line. The underlying mechanism of TNF-alpha suppression could be assigned to LcrV-mediated IL (IL)-10 production, because 1) LcrV induces IL-10 release in macrophages, 2) anti-IL-10 Ab treatment completely abrogated TNF-alpha suppression, and 3) TNF-alpha suppression was absent in LcrV-treated macrophages of IL-10-deficient (IL-10-/-) mice. The relevance of LcrV-mediated immunosuppression for the pathogenicity of yersiniae became evident by experimental infection of mice; in contrast to wild-type mice, IL-10-/- mice were highly resistant against Yersinia infection, as shown by lower bacterial load in spleen and liver, absent abscess formation in these organs, and survival.     

Local administration of interleukin-1beta for the treatment of lung abscesses induces neutrophil activation and changes in proinflammation cytokine production

Interleukin-1 (IL-1) is a potent immunostimulatory molecule with broad range biological activity that limits its systemic application in humans. Alternatively, IL-1 can be applied locally, directly to the inflammatory site for stimulation of local defense mechanisms, without activating an acute phase response. IL-1beta preparations have been successfully used for local therapy of patients with purulent bacterial lung abscesses who were resistant to usual antibiotic treatment. IL-1beta was applied directly to the abscess cavity at a concentration of 10 ng/ml, once a day for 7 days. Before IL-1beta administration, local leukocyte functional activity was significantly reduced compared to the same activity in neutrophils isolated from the peripheral blood of the same patient. Local application of IL-1beta led to increases in adhesion, chemotaxis, oxygen radical production and phagocytosis of abscess fluid neutrophils. After local IL-1beta treatment, the concentration of IL-8 and TNF-alpha in the abscess fluids increased, while in nearly all patients levels of endogenous IL-1beta decreased. Immunocytochemical analysis showed that IL-1beta increased the numbers of cytokine-producing cells and induced proinflammatory cytokine production by neutrophilic granulocytes. According to the results obtained, the mechanism of the local immunostimulatory activity by IL-1beta is associated with the significant activation of neutrophilic granulocyte functions and changes in cytokine production at the inflammatory site. IL-1beta can be used as a highly effective immunotherapeutic drug when applied locally at adequate immunostimulatory dose levels.