Comparative study of cytokine release by human peripheral blood mononuclear cells stimulated with Streptococcus pyogenes superantigenic erythrogenic toxins, heat-killed streptococci, and lipopolysaccharide

Sepsis therapies: learning from 30 years of failure of translational research to propose new leads

Sepsis has been identified by the World Health Organization (WHO) as a global health priority. There has been a tremendous effort to decipher underlying mechanisms responsible for organ failure and death, and to develop new treatments. Despite saving thousands of animals over the last three decades in multiple preclinical studies, no new effective drug has emerged that has clearly improved patient outcomes. In the present review, we analyze the reasons for this failure, focusing on the inclusion of inappropriate patients and the use of irrelevant animal models. We advocate against repeating the same mistakes and propose changes to the research paradigm. We discuss the long-term consequences of surviving sepsis and, finally, list some putative approaches-both old and new-that could help save lives and improve survivorship.

Analysis of Porcine Pro- and Anti-Inflammatory Cytokine Induction by S. suis In Vivo and In Vitro

Weaning piglets are susceptible to the invasive Streptococcus (S.) suis infection, which can result in septicemia. The aim of this study was to investigate the cytokine profile induced upon S. suis infection of blood, to determine the cellular sources of those cytokines, and to study the potential effects of the induced cytokines on bacterial killing. We measured TNF-α, IL-6, IFN-γ, IL-17A and IL-10 after an experimental intravenous infection with S. suis serotype 2 in vivo, and analyzed whole blood, peripheral blood mononuclear cells (PBMC) and separated leukocytes to identify the cytokine-producing cell type(s). In addition, we used a reconstituted whole blood assay to investigate the effect of TNF-α on bacterial killing in the presence of different S. suis-specific IgG levels. An increase in IL-6 and IL-10, but not in IFN-γ or IL-17A, was observed in two of three piglets with pronounced bacteremia 16 to 20 h after infection, but not in piglets with controlled bacteremia. Our results confirmed previous findings that S. suis induces TNF-α and IL-6 and could demonstrate that TNF-α is produced by monocytes in vitro. We further found that IL-10 induction resulted in reduced secretion of TNF-α and IL-6. Rapid induction of TNF-α was, however, not crucial for in vitro bacterial killing, not even in the absence of specific IgG.

Historical links between toxinology and immunology

Research on bacterial toxins is closely linked to the birth of immunology. Our understanding of the interaction of bacterial protein toxins with immune cells has helped to decipher immunopathology, develop preventive and curative treatments for infections, and propose anti-cancer immunotherapies. The link started when Behring and Kitasato demonstrated that serotherapy was effective against 'the strangling angel', namely diphtheria, and its dreadful toxin discovered by Roux and Yersin. The antitoxin treatment helped to save thousands of children. Glenny demonstrated the efficacy of the secondary immune response compared to the primary one. Ramon described anatoxins that allowed the elaboration of effective vaccines and discovered the use of adjuvant to boost the antibody response. Similar approaches were later made for the tetanus toxin. Studying antitoxin antibodies Ehrlich demonstrated, for the first time, the transfer of immunity from mother to newborns. In 1989 Marrack and Kappler coined the concept of 'superantigens' to characterize protein toxins that induce T-lymphocyte proliferation, and cytokine release by both T-lymphocytes and antigen presenting cells. More recently, immunotoxins have been designed to kill cancer cells targeted by either specific antibodies or cytokines. Finally, the action of IgE antibodies against toxins may explain their persistence through evolution despite their side effect in allergy.

Exotoxins and endotoxins: Inducers of inflammatory cytokines

Endotoxins and exotoxins are among the most potent bacterial inducers of cytokines. During infectious processes, the production of inflammatory cytokines including tumor necrosis factor (TNF), interleukin-1β (IL-1β), gamma interferon (IFNγ) and chemokines orchestrates the anti-infectious innate immune response. However, an overzealous production, leading up to a cytokine storm, can be deleterious and contributes to mortality consecutive to sepsis or toxic shock syndrome. Endotoxins of Gram-negative bacteria (lipopolysaccharide, LPS) are particularly inflammatory because they generate auto-amplificatory loops after activation of monocytes/macrophages. LPS and numerous pore-forming exotoxins also activate the inflammasome, the molecular platform that allows the release of mature IL-1β and IL-18. Among exotoxins, some behave as superantigens, and as such activate the release of cytokines by T-lymphocytes. In most cases, pre-exposure to exotoxins enhances the cytokine production induced by LPS and its lethality, whereas pre-exposure to endotoxin usually results in tolerance. In this review we recall the various steps, which, from the very early discovery of pyrogenicity induced by bacterial products, ended to the discovery of the endogenous pyrogen. Furthermore, we compare the specific characteristics of endotoxins and exotoxins in their capacity to induce inflammatory cytokines.

Clinical characteristics and outcomes of peritoneal dialysis-related peritonitis with different trends of change in effluent white cell count: a longitudinal study

BACKGROUND

Effluent white cell count (WCC) is among the important prognostic factors for peritonitis outcome, but its trend has never been studied. We aimed to explore the clinical characteristics and outcomes of peritonitis episodes having different trends in effluent WCC change in the first 5 days.

METHODS

For each peritonitis episode, we examined the patient's demographic and biochemical data, serial effluent WCC, and organisms cultured. Peritonitis-associated death and transfer to hemodialysis were defined as treatment failure.

RESULTS

Based on the trend of effluent WCC in the first 5 days, we divided 190 peritonitis episodes into group A (WCC persistently declined), group B (WCC declined after a transient increase), group C (WCC increased after a transient decline), and group D (WCC persistently increased). In group A, peritonitis was caused mostly by gram-positive organisms, and effluent WCC declined the most quickly, leading to a good prognosis. Although the elevation of effluent WCC was prolonged in group B, and the infections were, compared with those in group A, more often caused by gram-negative organisms, outcomes were not worse. In group C, the effluent WCC was more likely to be higher than 100/μL on day 5, and the infection was, compared with those in groups A and B, less likely to be caused by gram-positive organisms. Accordingly, membership in group C independently predicted the worst outcome of peritonitis even adjusted for age, sex, and causative organism.

CONCLUSIONS

Different trends of change in effluent WCC during the early stage of peritonitis represent different clinical patterns and outcomes. Further investigation for optimizing outcomes is required.

Regulatory role of GSK-3 β on NF- κ B, nitric oxide, and TNF- α in group A streptococcal infection

Group A streptococcus (GAS) imposes a great burden on humans. Efforts to minimize the associated morbidity and mortality represent a critical issue. Glycogen synthase kinase-3β (GSK-3β) is known to regulate inflammatory response in infectious diseases. However, the regulation of GSK-3β in GAS infection is still unknown. The present study investigates the interaction between GSK-3β, NF-κB, and possible related inflammatory mediators in vitro and in a mouse model. The results revealed that GAS could activate NF-κB, followed by an increased expression of inducible nitric oxide synthase (iNOS) and NO production in a murine macrophage cell line. Activation of GSK-3β occurred after GAS infection, and inhibition of GSK-3β reduced iNOS expression and NO production. Furthermore, GSK-3β inhibitors reduced NF-κB activation and subsequent TNF-α production, which indicates that GSK-3β acts upstream of NF-κB in GAS-infected macrophages. Similar to the in vitro findings, administration of GSK-3β inhibitor in an air pouch GAS infection mouse model significantly reduced the level of serum TNF-α and improved the survival rate. The inhibition of GSK-3β to moderate the inflammatory effect might be an alternative therapeutic strategy against GAS infection.

Expression dynamics of Toll-like receptors mRNA and cytokines in porcine peripheral blood mononuclear cells stimulated by bacterial lipopolysaccharide

The Toll-like receptor (TLR)4 is critical for the recognition of Gram-negative bacterial lipopolysaccharide (LPS) but in porcine peripheral blood mononuclear cells (PBMCs) it may cooperate with other TLRs and lead to the production of inflammatory cytokines. Therefore, we analyzed TLR1-10 mRNA expression in porcine PBMCs stimulated with LPS over time (1-48 h) by using quantitative real-time PCR and cytokine proteins level by ELISA in culture supernatant. TLR1-10 mRNA was detectable in porcine PBMCs. When compared with the control (non-stimulated), TLR1 mRNA were increased (p<0.05) at 3 h after challenge with 1 μg/ml LPS, whereas TLR1 and TLR2 mRNA were increased (p<0.01) at 6 h after challenge with 10 μg/ml LPS. TLR4 increased (p<0.001) at 3h after challenge with LPS and remained constant. TLR5 and TLR6 mRNA increased (p<0.05) at 9 h and 1 h after of LPS stimulation, respectively. The mRNA of CD14 and MD2 were increased (p<0.001) at 1h after LPS stimulation. Additionally, at most of the time analyzed, the mRNA expression increased with the dose of LPS. The LPS concentration had influence (p<0.05) on all the TLRs expression except TLR10; whereas time had effect (p<0.05) on all TLRs expression except TLR2, 3, 6 and 10. When compared to the control, the cytokines IL1b, IL8 and TNFα proteins were increased (p<0.001) immediately at 1 h after LPS stimulation and remained constant till 48 h. IL12b was increased (p<0.001) 12 h after challenge with 10 μg/ml of LPS. Although IL8 level was the highest, the higher (p<0.05) expression of all these inflammatory cytokines indicate that upon interacting with TLRs, LPS exerted inflammatory response in PBMCs through the production of Th1 type cytokines. The production of cytokines was influenced (p<0.001) by both the dose of LPS and the stimulation time. Hence, the porcine PBMCs are likely able to express all members of TLRs.

Bacterial superantigens enhance the in vitro proinflammatory response and in vivo lethality of the TLR2 agonist bacterial lipoprotein

Bacterial superantigens are Gram-positive exotoxins that induce proinflammatory cytokine release in vitro, cause lethal shock in vivo, and can be detected in the bloodstream of critically ill patients. They also have a powerful priming effect on the TLR4 agonist LPS. The aim of this study was to investigate the relationship between superantigens and the TLR2 agonist bacterial lipoprotein (BLP). Priming of human monocytes or PBMCs with superantigens significantly enhanced proinflammatory cytokine TNF-α and IL-6 release in response to BLP stimulation. The priming effect of superantigens could be blocked by inhibiting p38 MAPK during the priming phase as opposed to NF-κB or ERK inhibition. This was consistent with higher expression of the phosphorylated p38 after superantigen priming and BLP or LPS stimulation. C57BL/6 mice with superantigen priming (10 μg/mouse) when challenged with BLP (600 μg/mouse) exhibited substantially higher mortality (100%) compared with mice without superantigen priming (zero). Mice given superantigen alone did not demonstrate any signs of illness. Mice challenged with both superantigen and BLP had significantly higher levels of serum TNF-α and IL-6 compared with those of mice challenged with either agent alone. Depletion of the monocyte/macrophage subpopulation significantly reduced the mortality rate from 100 to 20% in superantigen-primed, BLP-challenged C57BL/6 mice, with a 5- to 10-fold decrease in serum TNF-α and IL-6. Our results demonstrate that bacterial superantigens enhance the in vitro proinflammatory cytokine release and in vivo lethality of BLP. This novel finding may help to explain the massive proinflammatory cytokine release seen in superantigen-mediated septic shock.

Lactobacilli reduce cell cytotoxicity caused by Streptococcus pyogenes by producing lactic acid that degrades the toxic component lipoteichoic acid

Lactobacilli are known to prevent colonization by many pathogens; nevertheless, the mechanisms of their protective effect are largely unknown. In this work, we investigated the role of lactobacilli during infection of epithelial cells with group A streptococci (GAS). GAS cause a variety of illnesses ranging from noninvasive disease to more severe invasive infections, such as necrotizing fasciitis and toxic shock-like syndrome. Invasion of deeper tissues is facilitated by GAS-induced apoptosis and cell death. We found that lactobacilli inhibit GAS-induced host cell cytotoxicity and shedding of the complement regulator CD46. Further, survival assays demonstrated that lactic acid secreted by lactobacilli is highly bactericidal toward GAS. In addition, lactic acid treatment of GAS, but not heat killing, prior to infection abolishes the cytotoxic effects against human cells. Since lipoteichoic acid (LTA) of GAS is heat resistant and cytotoxic, we explored the effects of lactic acid on LTA. By applying such an approach, we demonstrate that lactic acid reduces epithelial cell damage caused by GAS by degrading both secreted and cell-bound LTA. Taken together, our experiments reveal a mechanism by which lactobacilli prevent pathogen-induced host cell damage.

Characterization of pneumonia due to Streptococcus equi subsp. zooepidemicus in dogs

Streptococcus equi subsp. zooepidemicus has been linked to cases of acute fatal pneumonia in dogs in several countries. Outbreaks can occur in kenneled dog populations and result in significant levels of morbidity and mortality. This highly contagious disease is characterized by the sudden onset of clinical signs, including pyrexia, dyspnea, and hemorrhagic nasal discharge. The pathogenesis of S. equi subsp. zooepidemicus infection in dogs is poorly understood. This study systematically characterized the histopathological changes in the lungs of 39 dogs from a large rehoming shelter in London, United Kingdom; the dogs were infected with S. equi subsp. zooepidemicus. An objective scoring system demonstrated that S. equi subsp. zooepidemicus caused pneumonia in 26/39 (66.7%) dogs, and most of these dogs (17/26 [65.4%]) were classified as severe fibrino-suppurative, necrotizing, and hemorrhagic. Three recently described superantigen genes (szeF, szeN, and szeP) were detected by PCR in 17/47 (36.2%) of the S. equi subsp. zooepidemicus isolates; however, there was no association between the presence of these genes and the histopathological score. The lungs of S. equi subsp. zooepidemicus-infected dogs with severe respiratory signs and lung pathology did however have significantly higher mRNA levels of the proinflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and interleukin 8 (IL-8) than in uninfected controls, suggesting a role for an exuberant host immune response in the pathogenesis of this disease.

Streptococcus zooepidemicus: an emerging canine pathogen

Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) has caused several outbreaks of haemorrhagic pneumonia in dogs in recent years. This highly contagious and often fatal disease is characterised by sudden onset of clinical signs including pyrexia, dyspnoea and haemorrhagic nasal discharge. Post mortem examination typically reveals pulmonary haemorrhage and pleural effusion. Histopathology demonstrates fibrino-suppurative, necrotising and haemorrhagic pneumonia in most cases. The pathogenesis of S. zooepidemicus infection in dogs is incompletely understood. Bacterial virulence factors as well as host factors may contribute to the severe outcome. S. zooepidemicus occasionally causes zoonotic infections with potentially serious consequences. Canine vaccines for S. zooepidemicus are currently not available and prevention of the disease therefore relies on limiting bacterial spread by implementing stringent control measures in kennels. Further research, particularly sequence analysis of canine strains, is required to gain insights into epidemiology and pathogenesis of this emerging disease.

An early favorable outcome of streptococcal toxic shock syndrome may require a combination of antimicrobial and intravenous gamma globulin therapy together with activated protein C

Streptococcal toxic shock syndrome (STSS) associated with a group A beta hemolytic streptococcal infection was described 18 y ago. Since then, although the pathophysiology of the syndrome has been clarified, mortality can be as high as 80%. A middle-aged female developed STSS associated with a group A streptococcal pneumonia. Laboratory studies confirmed respiratory and renal failure as well as disseminated intravascular coagulation with a striking reduction in endogenous procoagulants. The patient, probably due to her HLA DRB1*14 haplotype was unable to generate anti-streptococcal antibodies. She was treated with appropriate antimicrobial therapy together with intravenous gamma globulin and drotrecogin or activated protein C. Her response to this combined therapy was accompanied by a rapid resolution of the multiorgan failure and correction of the accompanying disseminated intravascular coagulation. This rapid response to treatment supports the hypohesis that several host factors including the immune response and loss of procoagulants determine the development and severity of the toxic shock syndromes. Further studies with this combined approach appear warranted.

Rapid tissue factor induction by oral streptococci and monocyte-IL-1beta

The ability of pro-inflammatory cytokines to promote coagulation prompted the hypothesis that pro-inflammatory cytokines induced by oral streptococci might play a role in the pathogenesis of viridans endocarditis. We used supernatant fluids from peripheral blood mononuclear monocyte (PBMC) cultures, stimulated for just 4-6 hrs with representative streptococcal isolates, to study cytokines that promoted endothelial tissue factor (TF) activity. Neutralizing antibodies demonstrated that interleukin-1beta (IL-1beta) was a major early endothelial TF inducer, and that recombinant IL-1beta was comparable with the supernatant fluid in activity. IL-1beta-rich supernatant fluids from oral streptococci-stimulated or lipopolysaccharide-stimulated PBMC cultures up-regulated the expression of endothelial ICAM-1 and E-selectin. These molecules could help trap TF-producing monocytes or dendritic cells bearing streptococci at the site. Thus, the rapid IL-1beta-inducing capacity of oral streptococci could facilitate the early deposition of bacteria in fibrin clots and promote endocarditis.

Differences in innate immune responses upon stimulation with gram-positive and gram-negative bacteria

BACKGROUND AND OBJECTIVES

Host recognition pathways for gram-negative and gram-positive bacteria comprise pattern recognition receptors among which Toll-like receptors (TLRs) play a pivotal role. TLRs share common signaling pathways yet exhibit specificity as well. Periodontal disease is initiated and maintained in the first line by gram-negative but also gram-positive bacterial infection of the gingival sulcus. To date only limited information is available on whether gram-positive and gram-negative bacteria induce different host responses (strength or quality).

MATERIALS AND METHODS

To elucidate these differential effects we focused on proinflammatory cytokine releases by assessing ex vivo stimulation of whole blood with heat-killed gram-negative and gram-positive bacteria and thereof derived microbial products associated with distinct TLRs. Tumor necrosis factor-alpha and interleukin-8 release were measured in the supernatants by enzyme-linked immunosorbent assay. In addition, innate immune responses of peritoneal macrophages from mice lacking TLR2 and TLR4 were tested.

RESULTS

We observed that gram-negative and gram-positive species induced distinct patterns of cytokine production. Gram-negative species produced higher amounts of tumor necrosis factor-alpha while gram-positive species released higher amounts of the chemokine interleukin-8. Data from TLR knockout mice and TLR-transfected HEK cells revealed a somehow specific role of TLR4 and TLR2 for the recognition of gram-negative and gram-positive bacteria, respectively, an observation that goes along with the dominant recognition of the respective pathogen associated molecular patterns lipopolysaccharide and lipoteichoic acid.

CONCLUSIONS

The results show that gram-negative and gram-positive bacterial species induce different patterns of immunoregulatory activity, which might be the result of activation of different TLRs.

Evidence for cross-regulated cytokine response in human peripheral blood mononuclear cells exposed to whole gonococcal bacteria in vitro

Neisseria gonorrhoeae is an obligate human pathogen that represents a significant health concern, particularly in the developing world. Although generally associated with an acute inflammatory infection of urogenital epithelia cells, infections have been noted in multiple tissues and many infected individuals can become asymptomatic carriers. Few studies of immune response to N. gonorrhoeae infection in peripheral blood have evaluated the production of T helper cytokines (TH1/TH2) induced early after infection. We developed a quantitative realtime PCR assay based on the gonococcal rmpIII gene to monitor dose-response effects of infection on cytokine release from peripheral blood mononuclear cells (PBMCs). We observed upregulation of CD69 transcription and surface CD25 expression on lymphocytes, consistent with early T-cell activation. We observed dosage-dependent transcription of the chemotactic factor IL-8 and previously unreported activation of the chemoattractant MCP-2. Multiplex analysis of broad cytokine protein production revealed a differential increase in the TH1 and TH2 associated cytokines: IL-2, IL-4, IL-8, IL-10, IL-12, IFN-gamma, TNF-alpha and MCP-1. Markov models of protein accumulation implicated a cross-regulated response to infection, notably for IL-8, IL-10 and IL-12. Taken together, the cytokine profile we observed early in response to whole gonococcal bacteria was broader than has been previously described and may have relevance for the contribution of antagonistic signaling events early in infection and in understanding peripheral immune mechanisms engaged to control infection.

HIV-1 burden influences host response to co-infection with Neisseria gonorrhoeae in vitro

There is considerable evidence that co-infection with the sexually transmitted pathogen Neisseria gonorrhoeae (Gc) can increase the likelihood of both transmitting and acquiring HIV-1 worldwide. However, less information is available on how host immune response to co-infection differs with immune response to HIV-1 infection alone. To evaluate HIV-1 burden effects on host response to co-infection with Gc, we performed gene-expression profiling of human PBMCs infected over a broad range of viral titers (HIV-1 series) and upon exposure to a single infectious dose of Gc (HIV-1/Gc series). The transcriptional profiles differed substantially between each series (P < 0.0001). Major shifts in the transcriptional landscape were identified in contour plots based on fold stimulation and hierarchical clustering. Prominent regions of transcriptional activity were evaluated for statistical enrichment to identify up-regulated pathways associated with immune response, infection and T-cell stimulation. Notably, gene enrichment was dependent on HIV-1 burden and shifted during co-infection to reveal a disproportionate effect on lymphocyte signaling, apoptosis and proteasome activity. Further evaluation of these findings may help to better understand the role of viral burden in defining cellular contribution to host immune response upon co-infection with secondary sexually transmitted pathogens.

Staphylococcal enterotoxin A-induced hepatotoxicity is predominantly mediated by Fas ligand (CD95L)

OBJECTIVE

To determine the role of tumor necrosis factor alpha (TNF-alpha) and Fas ligand (FasL, CD95L) in superantigen-induced and endotoxin-induced liver injury.

SUMMARY BACKGROUND DATA

Gram-positive bacteria are increasingly common causes of sepsis and multiorgan failure, but the pathophysiologic mechanisms of superantigen-provoked hepatotoxicity remain elusive.

METHODS

Intravital fluorescence microscopy was used to study the liver microcirculation in mice challenged with superantigen (staphylococcal enterotoxin A, SEA) or endotoxin (lipopolysaccharide, LPS) combined with D-galactosamine.

RESULTS

Administration of 10 microg LPS and 50 microg SEA caused similar hepatocellular damage as determined by liver enzymes and apoptosis. Notably, TNF-alpha-deficient mice were completely protected against hepatic injury provoked by LPS, whereas no protection was observed in response to SEA. On the other hand, FasL-deficient mice were protected against liver injury induced by SEA, but no protection was found when challenged with LPS. LPS increased clear-cut leukocyte recruitment, whereas SEA had no significant effect on leukocyte responses in the liver microcirculation. Leukocyte responses to LPS were decreased by >56% in TNF-alpha gene-targeted animals. Moreover, antiadhesive therapy, ie, immunoneutralization of P-selectin, which is an effective inhibitor of leukocyte recruitment, protected against LPS-induced but not against SEA-induced hepatic damage.

CONCLUSIONS

These novel findings demonstrate that the mechanisms of hepatic injury in endotoxin-induced and superantigen-induced sepsis are principally different. On one hand, SEA-provoked hepatotoxicity is mediated by FasL and is not associated with leukocyte recruitment. On the other hand, liver damage provoked by LPS is mediated by TNF-alpha and characterized by prominent leukocyte responses. These data may facilitate development of more specific therapies against sepsis of different origins.

Toll-like receptors and the host defense against microbial pathogens: bringing specificity to the innate-immune system

Toll-like receptors (TLRs) have been identified as a major class of pattern-recognition receptors. Recognition of pathogen-associated molecular patterns (PAMPs) by TLRs, alone or in heterodimerization with other TLR or non-TLR receptors, induces signals responsible for the activation of genes important for an effective host defense, especially proinflammatory cytokines. Although a certain degree of redundancy exists between signals induced by the various TLRs, recent studies have identified intracellular pathways specific for individual TLRs. This leads to the release of cytokine profiles specific for particular PAMPs, and thus, TLRs confer a certain degree of specificity to the innate-immune response. In addition to the activation of the innate-immune response, TLR-mediated recognition represents a link between the innate- and acquired-immune systems, by inducing the maturation of dendritic cells and directing the T helper responses. Alternatively, recent data have also suggested TLR-mediated escape mechanisms used by certain pathogenic microorganisms, especially through TLR2 induction of anti-inflammatory cytokines. Finally, the crucial role of TLRs for the host defense against infections has been strengthened recently by the description of patients partially defective in the TLR-activation pathways.

Molecular characterization of the acute inflammatory response to infections with gram-negative versus gram-positive bacteria

Sepsis caused by gram-negative bacteria and that caused by gram-positive bacteria often manifest similar clinical features. We investigated plasma proinflammatory cytokine profiles in patients with sepsis due to gram-positive and gram-negative bacteria and studied the cytokine production and differential gene regulation of leukocytes stimulated ex vivo with Escherichia coli lipopolysaccharide or heat-killed Staphylococcus aureus. Concentrations of tumor necrosis factor alpha, interleukin 1 receptor antagonist (IL-1Ra), IL-8, IL-10, IL-18 binding protein, procalcitonin, and protein C in plasma did not differ between patients with sepsis due to gram-negative and gram-positive bacteria. However, plasma IL-1beta, IL-6, and IL-18 concentrations were significantly higher in patients with sepsis due to gram-positive bacteria. Ex vivo stimulation of whole blood with heat-killed S. aureus markedly increased IL-1beta and IL-18 levels more than E. coli lipopolysaccharide stimulation. Microarray analysis revealed at least 359 cross-validated probe sets (genes) significant at the P < 0.001 level whose expression discriminated among gram-negative-organism-stimulated, gram-positive-organism-stimulated, and unstimulated whole-blood leukocytes. The host inflammatory responses to gram-negative and gram-positive stimuli share some common response elements but also exhibit distinct patterns of cytokine appearance and leukocyte gene expression.

Staphylococcal and streptococcal superantigens: molecular, biological and clinical aspects

Superantigens (SAgs) include a class of certain bacterial and viral proteins exhibiting highly potent lymphocyte-transforming (mitogenic) activity towards human and or other mammalian T lymphocytes. Unlike conventional antigens, SAgs bind to certain regions of major histocompatibility complex (MHC) class II molecules of antigen-presenting cells (APCs) outside the classical antigen-binding groove and concomitantly bind in their native form to T cells at specific motifs of the variable region of the beta chain (Vbeta) of the T cell receptor (TcR). This interaction triggers the activation (proliferation) of the targeted T lymphocytes and leads to the in vivo or in vitro release of high amounts of various cytokines and other effectors by immune cells. Each SAg interacts specifically with a characteristic set of Vbeta motifs. The review summarizes our current knowledge on S. aureus and S. pyogenes superantigen proteins. The repertoire of the staphylococcal and streptococcal SAgs comprises 24 and 8 proteins, respectively. The staphylococcal SAgs include (i) the classical enterotoxins A, B, C (and antigenic variants), D, E, and the recently discovered enterotoxins G to Q, (ii) toxic shock syndrome toxin-1, (iii) exfoliatins A and B. The streptococcal SAgs include the classical pyrogenic exotoxins A and C and the newly identified pyrogenic toxins, G, H, I, J, SMEZ, and SSA. The structural and genomic aspects of these toxins and their molecular relatedness are described as well as the available 3-D crystal structure of some of them and that of certain of their complexes with MHC class II molecules and the TcR, respectively. The pathophysiological properties and clinical disorders related to these SAgs are reviewed.

The modulatory effects of prostaglandin-E on cytokine production by human peripheral blood mononuclear cells are independent of the prostaglandin subtype

The production of inflammatory mediators, relevant to (auto)immune diseases and chronic inflammatory conditions, can be modulated by dietary intake of n-3 and n-6 long chain polyunsaturated fatty acids (PUFAs). It was suggested that these effects are related to the formation of different series of eicosanoids, in particular prostaglandin-E (PGE). In this study we investigated whether prostaglandin subtypes metabolized from arachidonic acid (PGE2), dihomo-gamma-linolenic acid (PGE1) or eicosapentaenoic acid (PGE3) have different effects on T-cell proliferation and cytokine production in vitro. Freshly isolated human peripheral blood mononuclear cells (PBMC) were stimulated with concanavalin A (ConA) or lipopolysaccharide (LPS) in the presence or absence of exogenous PGE1, PGE2 or PGE3. We found that tumour necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma) and to a lesser extent interleukin (IL)-10 production was inhibited by all PGE-subtypes in ConA-stimulated PBMC concomitant with unaffected IL-2 levels. The modulated cytokine production of ConA stimulated cells was independent of T-cell proliferation. PGE2 and PGE1 moderately stimulated proliferation, while PGE3 inhibited the proliferative response to some extent. In LPS-stimulated PBMC, TNF-alpha production was inhibited by all PGE-subtypes, whereas IL-6 remained unaffected and IL-10 production was increased. Time course experiments on the effects of PGE-subtypes on cytokine production after ConA or LPS stimulation showed these effects to be time dependent, but indifferent of the prostaglandin subtype added. Overall, the modulatory effects of PGE on cytokine production were irrespective of the subtype. This may implicate that the immunomodulatory effects of PUFAs, with respect to cytokine production, are not caused by a shift in the subtype of PGE.

A modified ex vivo human whole blood model of infection for studying the pathogenesis of Neisseria meningitidis during septicemia

For the purpose of establishing a model to study host-bacteria interaction and virulence mechanisms of Neisseria meningitidis during the septic phase of disease a modified human whole blood model of infection is proposed. Compared to published whole blood models the current model was modified with respect to the initial number of viable bacteria (10(4) cfu ml(-1)), the anticoagulant used and the incubation time. The results obtained after incubation of a number of human blood samples from healthy volunteers for 24 h with serogroup B meningococci were in good agreement with findings reported from patients who suffered severe meningococcal disease.

Superantigen bacterial toxins: state of the art

Superantigens (SAgs) are viral and bacterial proteins exhibiting a highly potent polyclonal lymphocyte-proliferating activity for CD4(+), CD8(+) and sometimes gammadelta(+) T cells of human and (or) various animal species. Unlike conventional antigens, SAgs bind as unprocessed proteins to invariant regions of major histocompatibility complex (MHC) class II molecules on the surface of antigen-presenting cells (APCs) and to particular motifs of the variable region of the beta chain (Vbeta) of T-cell receptor (TcR) outside the antigen-binding groove. As a consequence, SAgs stimulate at nano-to picogram concentrations up to 10 to 30% of host T-cell repertoire while only one in 10(5)-10(6) T cells (0.01-0.0001%) are activated upon conventional antigenic peptide binding to TcR. SAg activation of an unusually high percentage of T lymphocytes initiates massive release of pro-inflammatory and other cytokines which play a pivotal role in the pathogenesis of the diseases provoked by SAg-producing microorganisms. We briefly describe in this review the molecular and biological properties of the bacterial superantigen toxins and mitogens identified in the past decade.

Infectious disease update

Many newly described or "re-emerging" infectious diseases may present to the dermatologist, often with potentially life-threatening implications. Prompt recognition and early intervention can greatly diminish the morbidity and mortality associated with these diseases.

Pyrogenicity and cytokine-inducing properties of Streptococcus pyogenes superantigens: comparative study of streptococcal mitogenic exotoxin Z and pyrogenic exotoxin A

Streptococcal mitogenic exotoxin Z (SMEZ), a superantigen derived from Streptococcus pyogenes, provoked expansion of human lymphocytes expressing the Vbeta 2, 4, 7 and 8 motifs of T-cell receptor. SMEZ was pyrogenic in rabbits and stimulated the expression of the T-cell activation markers CD69 and cutaneous lymphocyte-associated antigen. A variety of cytokines was released by human mononuclear leukocytes stimulated with SMEZ, which was 10-fold more active than streptococcal pyrogenic exotoxin A. Th2-derived cytokines were elicited only by superantigens and not by streptococcal cells.

What are the microbial components implicated in the pathogenesis of sepsis? Report on a symposium

Despite considerable efforts in the past quarter century to improve therapy for sepsis, mortality rates remain unacceptably high. Microbe-derived constituents can induce the host to produce many mediators that can contribute to immune dysregulation, tissue damage, and death. Although endotoxin-mediated events are clearly important in gram-negative infections, gram-positive bacteria can also play a dominant role. Understanding the interplay of microbial constituents and host immune or inflammatory responses prompted a meeting at Rockefeller University in May 1998. Participants discussed the relative merits of a "2-hit" hypothesis to explain the course of lethal septic shock and a "multihit" synergistic threshold hypothesis. Recommendations include the following: (1) developing animal models that closely mimic human sepsis; (2) further investigating antibiotic effects on bacteria; (3) assessing the relationships between endotoxin, prokaryotic DNA, and peptidoglycan (i.e., independent, additive, or synergistic) in inducing host responses; and (4) developing new strategies to improve outcomes. Studies are needed to better define which and how different microbial constituents lead to sepsis and to provide critical leads for therapeutic intervention.

Differential tumor necrosis factor alpha expression and release from peritoneal mouse macrophages in vitro in response to proliferating gram-positive versus gram-negative bacteria

Viable Escherichia coli and Staphylococcus aureus bacteria elicited markedly different in vitro tumor necrosis factor alpha (TNF-alpha) responses when placed in coculture with peritoneal murine macrophages. These include quantitative differences in TNF-alpha mRNA expression and corresponding protein product secretion as well as kinetic differences in the profiles of the TNF-alpha responses. Further, lipopolysaccharide (from E. coli) is a major contributing factor to these differences, as revealed by comparative experiments with endotoxin-responsive (C3Heb/FeJ) and endotoxin-hyporesponsive (C3H/HeJ) macrophages. Nevertheless, the eventual overall magnitude of the TNF-alpha secretion of macrophages in response to S. aureus was at least equivalent to that observed with E. coli, while appearing at time periods hours later than the E. coli-elicited TNF-alpha response. Both the magnitude and kinetic profile of the TNF-alpha responses were found to be relatively independent of the rate of bacterial proliferation, at least to the extent that similar results were observed with both viable and paraformaldehyde-killed microbes. Nevertheless, S. aureus treated in culture with the carbapenem antibiotic imipenem manifests markedly altered profiles of TNF-alpha response, with the appearance of an early TNF-alpha peak not seen with viable organisms, a finding strikingly similar to that recently reported by our laboratory from in vivo studies (R. Silverstein, J. G. Wood, Q. Xue, M. Norimatsu, D. L. Horn, and D. C. Morrison, Infect. Immun. 68:2301-2308, 2000). In contrast, imipenem treatment of E. coli-cocultured macrophages does not significantly alter the observed TNF-alpha response either in vitro or in vivo. In conclusion, our data support the concept that the host inflammatory response of cultured mouse macrophages in response to viable gram-positive versus gram-negative microbes exhibits distinctive characteristics and that these distinctions are, under some conditions, altered on subsequent bacterial killing, depending on the mode of killing. Of potential importance, these distinctive in vitro TNF-alpha profiles faithfully reflect circulating levels of TNF-alpha in infected mice. These results suggest that coculture of peritoneal macrophages with viable versus antibiotic-killed bacteria and subsequent assessment of cytokine response (TNF-alpha) may be of value in clarifying, and ultimately controlling, related host inflammatory responses in septic patients.

Identification of a novel gene cluster encoding staphylococcal exotoxin-like proteins: characterization of the prototypic gene and its protein product, SET1

We report the discovery of a novel genetic locus within Staphylococcus aureus that encodes a cluster of at least five exotoxin-like proteins. Designated the staphylococcal exotoxin-like genes 1 to 5 (set1 to set5), these open reading frames have between 38 and 53% homology to each other. All five proteins contain consensus sequences that are found in staphylococcal and streptococcal exotoxins and toxic shock syndrome toxin 1 (TSST-1). However, the SETs have only limited overall sequence homology to the enterotoxins and TSST-1 and thus represent a novel family of exotoxin-like proteins. The prototypic gene in this cluster, set1, has been cloned and expressed. Recombinant SET1 stimulated the production of interleukin-1beta, interleukin-6, and tumor necrosis factor alpha by human peripheral blood mononuclear cells. PCR analysis revealed that set1 was distributed among other strains of S. aureus but not in the other staphylococcal species examined. Sequence analysis of the set1 genes from different strains revealed at least three allelic variants. The protein products of these allelic variants displayed a 100-fold difference in their cytokine-inducing potency. The distribution of allelic variants of the set genes among strains of S. aureus may contribute to differences in the pathogenic potential of this bacterium.

Systemic activation of coagulation and fibrynolysis in a porcine model of serogroup A streptococcal shock

In a porcine model of Gram-positive sepsis, 28 juvenile pigs were studied to evaluate the effect of a continuous infusion of live serogroup A streptococci (GAS) on the activation of coagulation and fibrinolysis. Plasma levels of thrombin-antithrombin (TAT) complexes, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) activities were measured using commercially available kits. The continuous infusion of GAS [(3-5) x 10(8) colony-forming units/kg per h] caused early signs of severe septicaemia in the pigs, with pulmonary hypertension, systemic hypotension, reduced cardiac output and liver hypoperfusion, ultimately leading to shock with a high mortality. There was a sequential and ordered activation of the coagulation, fibrinolytic and antifibrinolytic systems. GAS infusion induced a gradual, maximally 2.5-fold increase in plasma TAT levels. Plasma t-PA activity levels peaked at 2 h (nine-fold increase), whereas the peak of PAI-1 activity was delayed (eight-fold increase at 4 h). These findings are similar to changes observed during endotoxin infusion. This procoagulant state favours disseminated intravascular coagulation and microthrombus formation, ultimately threatening tissue viability.

Streptococcal toxic shock syndrome associated with necrotizing fasciitis

Streptococcal toxic shock syndrome (strep TSS) with associated necrotizing fasciitis is a rapidly progressive process that kills 30-60% of patients in 72-96 h. Violaceous bullae, hypotension, fever, and evidence of organ failure are late clinical manifestations. Thus, the challenge to clinicians is to make an early diagnosis and to intervene with aggressive fluid replacement, emergent surgical debridement, and general supportive measures. Superantigens such as pyrogenic exotoxin A interact with monocytes and T lymphocytes in unique ways, resulting in T-cell proliferation and watershed production of monokines (e.g. tumor necrosis factor alpha, interleukin 1, interleukin 6), and lymphokines (e.g. tumor necrosis factor beta, interleukin 2, and gamma-interferon). Penicillin, though efficacious in mild Streptococcus pyogenes infection, is less effective in severe infections because of its short postantibiotic effect, inoculum effect, and reduced activity against stationary-phase organisms. Emerging treatments for strep TSS include clindamycin and intravenous gamma-globulin.

Systemic bacterial invasion induced by sleep deprivation

Profound sleep disruption in humans is generally believed to cause health impairments. Through comparative research, specific physical effects and underlying mechanisms altered by sleep deprivation are being elucidated. Studies of sleep-deprived animals previously have shown a progressive, chronic negative energy balance and gradual deterioration of health, which culminate in fatal bloodstream infection without an infectious focus. The present study investigated the conditions antecedent to advanced morbidity in sleep-deprived rats by determining the time course and distribution of live microorganisms in body tissues that are normally sterile. The tissues cultured for microbial growth included the blood, four major organs, six regional lymph nodes, the intestine, and the skin. The principal finding was early infection of the mesenteric lymph nodes by bacteria presumably translocated from the intestine and bacterial migration to and transient infection of extraintestinal sites. Presence of pathogenic microorganisms and their toxins in tissues constitutes a septic burden and chronic antigenic challenge for the host. Bacterial translocation and pathogenic sequelae provide mechanisms by which sleep deprivation appears to adversely affect health.

Cytokine secretion by stimulated monocytes depends on the growth phase and heat treatment of bacteria: a comparative study between lactic acid bacteria and invasive pathogens

The consumption of food containing lactic acid bacteria (LAB) has been shown to exert immunomodulatory effects in humans. The specific cellular interaction of these bacteria with immuno-competent cells has not yet been fully understood. Since the TNF-alpha secretion of stimulated monocytes is an important initial response to a bacterial challenge, we investigated the potential of LAB originating from the human intestine or fermented food in comparison to the effect of invasive pathogens. The challenge of monocytes with three LAB strains, Listeria monocytogenes or enterohaemorrhagic Escherichia coli (EHEC) elicited a strain specific, dose-dependent biphasic TNF-alpha secretion. The concentration (EDmax) of bacteria or bacterial cell wall components necessary to induce maximal TNF-alpha secretion (TNFmax) by monocytes was mathematically approximated. It was shown for exponentially growing LAB strains that the maximal TNF-alpha secretion (TNFmax) was stronger (57 to 78%) upon stimulation with living bacteria than with heat killed cells. In contrast to log-phase bacteria, the maximal TNF-alpha secretion of monocytes (TNFmax) was higher (15 to 55%) after the stimulation with heat killed, stationary-phase bacteria when compared to that of live LAB. Thus, monocyte stimulation was clearly affected by the growth phase of bacteria. Purified cell walls of LAB strains revealed only a limited potential for monocyte stimulation. LPS exhibited a higher capacity to stimulate monocytes than purified gram positive cell walls or muramyldipeptide. In comparison to pathogenic bacteria, the maximal secretory TNF-alpha response (TNFmax) was up to 2 fold higher with LAB strains. In general, the amount of bacteria (EDmax) necessary to induce maximal TNF-alpha secretion (TNFmax) was approximately 1 to 3 log higher for heat killed bacteria when compared to live bacterial cells illustrating the significant lower potential of heat killed bacteria to activate monocytes.

Activation of human peripheral blood mononuclear cells by nonpathogenic bacteria in vitro: evidence of NK cells as primary targets

The interaction of commensal bacteria with immunocompetent cells may occur in definite compartments of the mucosal immune system, as limited translocation through the epithelial barrier cannot be excluded. In this study the stimulation of human peripheral blood mononuclear cells and purified lymphocyte subsets by nonpathogenic gram-positive lactobacilli (Lactobacillus johnsonii and Lactobacillus sakei) and gram-negative Escherichia coli was investigated. The various bacterial strains induced a differential cytokine pattern. Whereas L. johnsonii and L. sakei strongly induced gamma interferon (IFN-gamma) and interleukin-12 (IL-12), E. coli and lipopolysaccharide (LPS) preferentially induced IL-10 after 16 h of stimulation. Expression of activation antigens CD69 and CD25 was observed on (CD3(-) CD56(+)) natural killer (NK) cells after stimulation of total human peripheral blood mononuclear cells. All bacteria mediated the proliferation of human peripheral blood mononuclear cells, and the strongest proliferative response was observed with L. johnsonii. Purified CD4(+), CD8(+), and CD19(+) lymphocyte subsets were not activated upon bacterial stimulation but showed normal response to a mitogenic stimulus. In contrast, purified NK cells upregulated the IL-2Ralpha chain (CD25) and underwent proliferation when stimulated by L. johnsonii. E. coli and LPS were less effective in inducing proliferation. Expression of CD25 or secretion of IFN-gamma from purified NK cells was significantly increased in the presence of bacterially primed macrophages, indicating that full activation required both bacterium- and cell contact-based signals derived from accessory cells.

Streptococcal histone induces murine macrophages To produce interleukin-1 and tumor necrosis factor alpha

The histone-like protein (HlpA) is highly conserved among streptococci. After lysis of streptococci in infected tissues, HlpA can enter the bloodstream and bind to proteoglycans in the glomerular capillaries of kidneys, where it can react with antibodies or stimulate host cell receptors. Deposits of streptococcal antigens in tissues have been associated with localized acute inflammation. In this study, we measured the ability of purified HlpA (5 to 100 microg/ml), from Streptococcus mitis, to induce the production of proinflammatory cytokines by cultured, murine peritoneal macrophages. The release of tumor necrosis factor alpha (TNF-alpha) and interleukin-1 (IL-1) was time and concentration dependent and was not diminished by the presence of polymyxin B. Exposure of macrophages to a mixture of HlpA and lipoteichoic acid resulted in a synergistic response in the production of both TNF-alpha and IL-1. Stimulation with a mixture of HlpA and heparin resulted in reduced cytokine production (50% less IL-1 and 76% less TNF-alpha) compared to that by cells incubated with HlpA alone. The inclusion of antibodies specific to HlpA in macrophage cultures during stimulation with HlpA did not affect the quantity of TNF-alpha or IL-1 produced. These observations suggest that streptococcal histone may contribute to tissue injury at infection sites by promoting monocytes/macrophages to synthesize and release cytokines that initiate and exacerbate inflammation. Streptococcus pyogenes, which can infect tissues in enormous numbers, may release sufficient amounts of HlpA to reach the kidneys and cause acute poststreptococcal glomerulonephritis.

Immunoglobulin A1 protease, an exoenzyme of pathogenic Neisseriae, is a potent inducer of proinflammatory cytokines

A characteristic of human pathogenic Neisseriae is the production and secretion of an immunoglobulin (Ig)A1-specific serine protease (IgA1 protease) that cleaves preferentially human IgA1 and other target proteins. Here we show a novel function for native IgA1 protease, i.e., the induction of proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, and IL-8 from peripheral blood mononuclear cells. The capacity of IgA1 protease to elicit such cytokine responses in monocytes was enhanced in the presence of T lymphocytes. IgA1 protease did not induce the regulatory cytokine IL-10, which was, however, found in response to lipopolysaccharide and phytohemagglutinin. The immunomodulatory effects caused by IgA1 protease require a native form of the enzyme, and denaturation abolished cytokine induction. However, the proteolytic activity is not required for the cytokine induction by IgA1 protease. Our results indicate that IgA1 protease exhibits important immunostimulatory properties and may contribute substantially to the pathogenesis of neisserial infections by inducing large amounts of TNF-alpha and other proinflammatory cytokines. In particular, IgA1 protease may represent a key virulence determinant of bacterial meningitis.

Therapeutic Approaches to Streptococcal Toxic Shock Syndrome

The streptococcal toxic shock syndrome (STSS) is a severe, life-threatening condition characterized by hypotension and multiorgan system dysfunction associated with infection by the group A Streptococcus (GAS) or rarely by streptococci of other Lancefield serogroups. It is associated with a soft tissue infection, such as necrotizing fasciitis, in about half of the cases; the remainder are secondary to a variety of other invasive and noninvasive GAS infections. Although the pathophysiology of STSS is not yet fully understood, there are compelling reasons to believe that the syndrome results at least in part from the action of the streptococcal pyrogenic exotoxins, which act as superantigens. Patients with STSS should be admitted to an intensive care unit for support of cardiovascular, respiratory, and renal function as required. In experimental models of overwhelming GAS infection, clindamycin has greater efficacy than penicillin, and therapy with this agent is recommended. Penicillin, to which GAS are uniformly susceptible, may be used in addition to clindamycin. Limited clinical experience, most of which is anecdotal, suggests marked improvement in some STSS patients after administration of intravenous immunoglobulin. Even in the absence of conclusive data, the potential benefits of intravenous immunoglobulin in this highly lethal disease make its use reasonable in life-threatening cases. Other experimental approaches are also discussed, such as the use of anti-tumor necrosis factor monoclonal antibodies and plasmapheresis.

Clinical gram-positive sepsis: does it fundamentally differ from gram-negative bacterial sepsis?

OBJECTIVE

To review the basic differences between gram-positive and gram-negative sepsis and to assess the effect of these differences on current and future therapeutic strategies for sepsis.

DESIGN

Literature review of the past 30 yrs of laboratory and clinical reports that analyze the microbial aspects of sepsis and the immunologic response to systemic infection.

RESULTS

The increasing prevalence of sepsis from gram-positive bacterial pathogens necessitates reevaluation of many of the basic assumptions about the molecular pathogenesis of septic shock. It has been assumed that the initiation of the systemic inflammatory response with activation of the proinflammatory cytokine networks and other mediators results in a similar pathophysiologic process, regardless of the causative microbic pathogen. Yet, there is increasing experimental evidence that fundamental differences exist in the host response to gram-positive bacterial pathogens compared with the host response to gram-negative organisms. Systemic immune activation during sepsis may promote the clearance of the microbic pathogen; however, generalized inflammation also contributes to the pathogenesis of septic shock. The balance between these beneficial and deleterious effects may differ between gram-positive and gram-negative pathogens.

CONCLUSIONS

Results of antimediator therapies in clinical trials in septic shock are inconclusive but suggest that the response may differ, depending on the type of microbic pathogen. The immune-mediated pathophysiologic mechanisms that underlie gram-positive sepsis and the potential interactions between the infecting microorganism and efficacy of anticytokine therapies require further investigation. Treatment strategies that explain the causative organism may be necessary for optimal use of immunoadjuvants in the future.

Erythrogenic toxin type B and its precursor isolated from nephritogenic streptococci induce leukocyte infiltration in normal rat kidneys

BACKGROUND

Leukocyte infiltration is a common feature in renal biopsies from patients with acute poststreptococcal glomerulonephritis (APSGN). Cationic streptococcal erythrogenic toxin type B (ETB) and its precursor (ETBP) have been implicated in the pathogenesis of the disease, and the presence of ETB has been evidenced in renal biopsies from patients with APSGN. The present studies were performed to determine the effect of the ETBP and ETB on renal leukocyte infiltration and the mechanism(s) implicated in the phenomenon.

METHODS

Male Sprague-Dawley rats were injected intrarenally with 100 microg of ETB or ETBP. Animals were sacrificed at 1, 6 and 24 h after injection and renal samples were studied by indirect immunofluorescence for the presence of leukocyte common antigen (LCA+) cells, C3, monocyte chemotactic protein-1 (MCP-1) and intercellular adhesion molecule-(ICAM-1), and by direct immunofluorescence for the presence of immunoglobulins. ETB and ETBP were tested for chemotactic effect and migration inhibition factor (MIF) activity by chemotaxis under agarose and agarose microdroplet methods, respectively. Streptococcal proteins were also tested for the capacity to induce MIF activity in rat glomerular cultures. To test for the influence of cationic charge on renal LCA+ cell infiltration, rats were injected with cationized ferritin or polyethyleneimine (PEI) and sacrificed 1 h later.

RESULTS

An increased number of LCA+ cells was found in glomeruli and interstitial areas in ETB- or ETBP-injected animals. ETB and ETBP showed chemotactic and MIF activity on neutrophils and macrophages, and ETBP induced MIF activity in supernatants of glomerular cultures. Data obtained from C3, MCP-1, ICAM-1 or immunoglobulin renal staining in experimental animals were not significantly different when compared to control values. Cationized compounds failed to induce LCA+ cell infiltration; however, an increased number of glomerular LCA+ cells was observed after PEI perfusion.

CONCLUSIONS

ETB and ETBP induce renal LCA+ cell infiltration during a short period after intrarenal injection, and this finding could be mediated by chemotactic and MIF activities. These observations could be relevant in the early events of pathogenesis of APSGN.