Role of alpha(2)-macroglobulin in fever and cytokine responses induced by lipopolysaccharide in mice

Alpha(2)-macroglobulin (alpha(2)M) is not only a proteinase inhibitor in mammals, but it is also a specific cytokine carrier that binds pro- and anti-inflammatory cytokines implicated in fever, including interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha (TNF-alpha). To define the role of alpha(2)M in regulation of febrile and cytokine responses, wild-type mice and mice deficient in alpha(2)M (alpha(2)M -/-) were injected with lipopolysaccharide (LPS). Changes in body temperature as well as plasma levels of IL-1beta, IL-6, and TNF-alpha and hepatic TNF-alpha mRNA level during fever in alpha(2)M -/- mice were compared with those in wild-type control mice. The alpha(2)M -/- mice developed a short-term markedly attenuated (ANOVA, P < 0.05) fever in response to LPS (2.5 mg/kg ip) compared with the wild-type mice. At 1.5 h after injection of LPS, the plasma concentration of TNF-alpha, but not IL-1beta or IL-6, was significantly lower (by 58%) in the alpha(2)M -/- mice compared with their wild-type controls (ANOVA, P < 0.05). There was no difference in hepatic TNF-alpha mRNA levels between alpha(2)M -/- and wild-type mice 1.5 h after injection of LPS. These data support the hypotheses that 1) alpha(2)M is important for the normal development of LPS-induced fever and 2) a putative mechanism of alpha(2)M involvement in fever is through the inhibition of TNF-alpha clearance. These findings indicate a novel physiological role for alpha(2)M.     

Inflammatory cytokine production in interferon-gamma-primed mice, challenged with lipopolysaccharide. Inhibition by SK&F 86002 and interleukin-1 beta-converting enzyme inhibitor

Mice challenged with lipopolysaccharide (LPS) produce variable serum levels of pro-inflammatory cytokines, and particularly low levels of interleukin-1 beta (IL-1 beta). Interferon-gamma (IFN-gamma) has been shown to be an important mediator of bacteria-induced hypersensitivity to LPS in mice. In the present study, we show that mice pretreated with IFN-gamma exhibit an enhanced capacity to produce serum IL-1 beta, IL-1 alpha, tumour necrosis factor (TNF-alpha) as well as IL-6 in response to LPS. Priming with intraperitoneal (i.p.) injection of 15 mg rat recombinant IFN-gamma, 18 hours prior to the i.p. LPS (300 mg) challenge resulted in a 4-fold increase in the LPS-stimulated release of IL-1 beta and a 2- to 7-fold increase in the release of IL-1 alpha, TNF-alpha, as well as IL-6 into the serum. LPS induced a concentration-dependent increase in the release of IL-1 beta in isolated peritoneal macrophages from IFN-gamma-primed mice whereas macrophages from unprimed mice released minute amounts of IL-1 beta. In addition, nigericin markedly enhanced the release of IL-1 beta in unprimed mice but not in macrophages from IFN-gamma primed mice. The cytokine synthesis inhibitor SK&F 86002, administered per os (100 mg/kg), 1 hour prior to LPS challenge, strongly inhibited the rise in serum levels of the four cytokines. Furthermore, treatment with the IL-1 beta converting enzyme (ICE) specific reversible inhibitor YVAD-CHO resulted in a sharp dose- and time-dependent inhibition of IL-1 beta secretion in the serum, whereas the other cytokines were not affected. In conclusion, IFN-gamma priming strongly potentiates the release of proinflammatory cytokines in the serum of mice as compared to LPS stimulation alone, and provides therefore a useful way to test the in vivo potency and selectivity of cytokine synthesis inhibitors.     

Neutralization of IL-18 reduces neutrophil tissue accumulation and protects mice against lethal Escherichia coli and Salmonella typhimurium endotoxemia

In addition to stimulating IFN-gamma synthesis, IL-18 also possesses inflammatory effects by inducing synthesis of the proinflammatory cytokines TNF and IL-1beta and the chemokines IL-8 and macrophage inflammatory protein-1alpha. We hypothesized that neutralization of IL-18 would have a beneficial effect in lethal endotoxemia in mice. IL-1beta converting enzyme (ICE)-deficient mice, lacking the ability to process mature IL-18 and IL-1beta, were completely resistant to lethal endotoxemia induced by LPS derived from either Escherichia coli or Salmonella typhimurium. In contrast, both wild-type and IL-1beta-/- mice were equally susceptible to the lethal effects of LPS, implicating that absence of mature IL-18 or IFN-gamma but not IL-1beta in ICE-/- mice is responsible for this resistance. However, IFN-gamma-deficient mice were not resistant to S. typhimurium LPS, suggesting an IFN-gamma-independent role for IL-18. Anti-IL-18 Abs protected mice against a lethal injection of either LPS. Anti-IL-18 treatment also reduced neutrophil accumulation in liver and lungs. The increased survival was accompanied by decreased levels of IFN-gamma and macrophage inflammatory protein-2 in anti-IL-18-treated animals challenged with E. coli LPS, whereas IFN-gamma and TNF concentrations were decreased in treated mice challenged with S. typhimurium. In conclusion, neutralization of IL-18 during lethal endotoxemia protects mice against lethal effects of LPS. This protection is partly mediated through inhibition of IFN-gamma production, but mechanisms involving decreased neutrophil-mediated tissue damage due to the reduction of either chemokines (E. coli LPS) or TNF (S. typhimurium LPS) synthesis by anti-IL-18 treatment may also be involved.     

Surfactant protein A inhibits alveolar macrophage cytokine production by CD14-independent pathway

The lung collectin surfactant protein A (SP-A) has both anti-inflammatory and prophagocytic activities. We and others previously showed that SP-A inhibits the macrophage production of tumor necrosis factor (TNF)-alpha stimulated by the gram-negative bacterial component LPS. We propose that SP-A decreases the production of proinflammatory cytokines by alveolar macrophages via a CD14-independent mechanism. SP-A inhibited LPS-simulated TNF-alpha production in rat and mouse macrophages in the presence and absence of serum (72% and 42% inhibition, respectively). In addition, SP-A inhibited LPS-induced mRNA levels for TNF-alpha, IL-1 alpha, and IL-1 beta as well as NF-kappa B DNA binding activity. SP-A also diminished ultrapure LPS-stimulated TNF-alpha produced by wild-type and CD14-null mouse alveolar macrophages by 58% and 88%, respectively. Additionally, SP-A inhibited TNF-alpha stimulated by PMA in both wild-type and TLR4-mutant macrophages. These data suggest that SP-A inhibits inflammatory cytokine production in a CD14-independent manner and also by mechanisms independent of the LPS signaling pathway.     

Effects of IL-10 and age on IL-6, IL-1beta, and TNF-alpha responses in mouse skeletal and cardiac muscle to an acute inflammatory insult.

Exaggerated proinflammatory cytokine responses can be observed with aging, and reduced levels of the anti-inflammatory cytokine IL-10 may contribute to these responses. IL-10 can reduce IL-6, IL-1beta, and TNF-alpha expression in nonmuscle tissues; however, no studies have examined the combined effects of IL-10 and age on cytokine responses in skeletal and cardiac muscle. These experiments tested the hypothesis that the absence of IL-10, in vivo, is associated with greater IL-6, TNF-alpha, and IL-1beta responses to an inflammatory challenge in skeletal and cardiac muscle and that aging exaggerates these responses. We compared IL-6, IL-1beta, and TNF-alpha mRNA and protein levels in skeletal and cardiac muscle of young (4 mo) and mature (10-11 mo) wild-type (IL-10(+/+)) and IL-10 deficient (IL-10(-/-)) mice following LPS. Skeletal and cardiac IL-6 mRNA and protein were elevated by LPS for IL-10(+/+) and IL-10(-/-) mice with greater responses in the IL-10(-/-) mice (P < 0.01). In skeletal muscle these effects were greater in mature than young mice (P < 0.01). IL-1beta mRNA and protein responses to LPS were greater in cardiac muscle of young but not mature IL-10(-/-) mice compared with IL-10(+/+) (P < 0.01). However, IL-1beta responses were greater in mature than young mice, but only in IL-10(+/+) groups (P < 0.05). The absence of IL-10 was associated with higher TNF-alpha protein levels in cardiac muscle (P < 0.05). The results provide the first in vivo evidence that the absence of IL-10 is associated with a greater IL-6 response to LPS in skeletal and cardiac muscles, and in skeletal muscle aging further exaggerates these responses.     

Neutrophil leukocyte emigration induced by endotoxin. Mediator roles of interleukin 1 and tumor necrosis factor alpha 1

The hypothesis that cytokines mediate neutrophil emigration induced by endotoxin (LPS) was studied by examining the potency, the kinetics of neutrophil emigration, and the tachyphylaxis of intradermal sites with IL-1, TNF-alpha and LPS. Human rIL-1 alpha and IL-1 beta, synthetic lipid A, and LPS were several orders of magnitude more potent than human rTNF. The kinetic profiles of neutrophil emigration induced by IL-1 alpha, TNF, and LPS were characterized by minimal emigration in the first 30 min, followed by rapid and transient emigration. After the injection of LPS, the onset and the time at which the rate of emigration was maximal consistently appeared 30 min later than IL-alpha or TNF, suggesting that neutrophil emigration in response to LPS was mediated by a locally generated cytokine. IL-1 and TNF were then examined as potential secondary mediators of LPS-induced emigration by comparing the patterns of tachyphylaxis between LPS and IL-1 alpha or TNF; i.e., the magnitude of neutrophil emigration into inflammatory sites was compared with sites injected 6 h previously (desensitizing injections) with a cytokine or with LPS. Tachyphylaxis was dose dependent with each and also between the IL-1 species; therefore, when tachyphylaxis between the cytokines and LPS was examined, relatively higher doses were selected for the desensitizing injections than for the test injections. With this approach, desensitizing injections of IL-1 alpha diminished the neutrophil accumulation after LPS, and LPS also desensitized sites to IL-1 alpha. However, tachyphylaxis was not observed between TNF and LPS, or between TNF and IL-1 alpha. These data suggest that IL-1, but not TNF, is a potential mediator of LPS-induced neutrophil emigration.     

Vaccinia virus infection attenuates innate immune responses and antigen presentation by epidermal dendritic cells

Langerhans cells (LCs) are antigen-presenting cells in the skin that play sentinel roles in host immune defense by secreting proinflammatory molecules and activating T cells. Here we studied the interaction of vaccinia virus with XS52 cells, a murine epidermis-derived dendritic cell line that serves as a surrogate model for LCs. We found that vaccinia virus productively infects XS52 cells, yet this infection displays an atypical response to anti-poxvirus agents. Whereas adenosine N1-oxide blocked virus production and viral protein synthesis during a synchronous infection, cytosine arabinoside had no effect at concentrations sufficient to prevent virus replication in BSC40 monkey kidney cells. Vaccinia virus infection of XS52 cells not only failed to elicit the production of various cytokines, including tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), IL-6, IL-10, IL-12 p40, alpha interferon (IFN-alpha), and IFN-gamma, it actively inhibited the production of proinflammatory cytokines TNF-alpha and IL-6 by XS52 cells in response to exogenous lipopolysaccharide (LPS) or poly(I:C). Infection with a vaccinia virus mutant lacking the E3L gene resulted in TNF-alpha secretion in the absence of applied stimuli. Infection of XS52 cells or BSC40 cells with the DeltaE3L virus, but not wild-type vaccinia virus, triggered proteolytic decay of IkappaBalpha. These results suggest a novel role for the E3L protein as an antagonist of the NF-kappaB signaling pathway. DeltaE3L-infected XS52 cells secreted higher levels of TNF-alpha and IL-6 in response to LPS and poly(I:C) than did cells infected with the wild-type virus. XS52 cells were productively infected by a vaccinia virus mutant lacking the K1L gene. DeltaK1L-infected cells secreted higher levels of TNF-alpha and IL-6 in response to LPS than wild-type virus-infected cells. Vaccinia virus infection of primary LCs harvested from mouse epidermis was nonpermissive, although a viral reporter protein was expressed in the infected LCs. Vaccinia virus infection of primary LCs strongly inhibited their capacity for antigen-specific activation of T cells. Our results highlight suppression of the skin immune response as a feature of orthopoxvirus infection.     

Cutting edge: TNF-alpha-converting enzyme (TACE/ADAM17) inactivation in mouse myeloid cells prevents lethality from endotoxin shock

TNF-alpha, a potent proinflammatory cytokine, is synthesized as a membrane-anchored precursor and proteolytically released from cells. Soluble TNF is the primary mediator of pathologies such as rheumatoid arthritis, Crohn's disease, and endotoxin shock. The TNF-alpha converting enzyme (TACE), a disintegrin and metalloprotease 17 (ADAM17), has emerged as the best candidate TNF sheddase, but other proteinases can also release TNF. Because TACE-deficient mice die shortly after birth, we generated conditional TACE-deficient mice to address whether TACE is the relevant sheddase for TNF in adult mice. In this study, we report that TACE inactivation in myeloid cells or temporal inactivation at 6 wk offers strong protection from endotoxin shock lethality in mice by preventing increased TNF serum levels. These findings corroborate that TACE is the major endotoxin-stimulated TNF sheddase in mouse myeloid cells in vivo, thereby further validating TACE as a principal target for the treatment of TNF-dependent pathologies.     

Interleukin-17 acts independently of TNF-alpha under arthritic conditions

The proinflammatory T cell cytokine IL-17 is a potent inducer of other cytokines such as IL-1 and TNF-alpha. The contribution of TNF in IL-17-induced joint inflammation is unclear. In this work we demonstrate using TNF-alpha-deficient mice that TNF-alpha is required in IL-17-induced joint pathology under naive conditions in vivo. However, overexpression of IL-17 aggravated K/BxN serum transfer arthritis to a similar degree in TNF-alpha-deficient mice and their wild-type counterparts, indicating that the TNF dependency of IL-17-induced pathology is lost under arthritic conditions. Also, during the course of the streptococcal cell wall-induced arthritis model, IL-17 was able to enhance inflammation and cartilage damage in the absence of TNF. Additional blocking of IL-1 during IL-17-enhanced streptococcal cell wall-induced arthritis did not reduce joint pathology in TNF-deficient mice, indicating that IL-1 is not responsible for this loss of TNF dependency. These data provide further understanding of the cytokine interplay during inflammation and demonstrate that, despite a strong TNF dependency under naive conditions, IL-17 acts independently of TNF under arthritic conditions.     

Further characterization of high mobility group box 1 (HMGB1) as a proinflammatory cytokine: central nervous system effects

High mobility group box 1 (HMGB1), an abundant, highly conserved cellular protein, is widely known as a nuclear DNA-binding protein. HMGB1 has been recently implicated as a proinflammatory cytokine because of its role as a late mediator of endotoxin lethality and ability to stimulate release of proinflammatory cytokines from monocytes. Production of central cytokines is a critical step in the pathway by which endotoxin and peripheral proinflammatory cytokines, including interleukin-1beta (IL-1) and tumor necrosis factor-alpha (TNF), produce sickness behaviors and fever. Intracerebroventricular (ICV) administration of HMGB1 has been shown to increase TNF expression in mouse brain and induce aphagia and taste aversion. Here we show that ICV injections of HMGB1 induce fever and hypothalamic IL-1 in rats. Furthermore, we show that intrathecal administration of HMGB1 produces mechanical allodynia (lowering of the response threshold to calibrated stimuli). Finally, while endotoxin (lipopolysaccharide, LPS) administration elevates IL-1 and TNF mRNA in various brain regions, HMGB1 mRNA is unchanged. It remains possible that HMGB1 protein is released in brain in response to LPS. Nonetheless, these data suggest that HMGB1 may play a role as an endogenous pyrogen and support the concept that HMGB1 has proinflammatory characteristics within the central nervous system.     

Essential role for IL-10 in resistance to lipopolysaccharide-induced preterm labor in mice

IL-10 is highly expressed in the uterus and placenta and is implicated in controlling inflammation-induced pathologies of pregnancy. To investigate the role of IL-10 in regulating preterm labor, the response of IL-10 null mutant mice to low-dose LPS in late gestation was evaluated. When IL-10 null mutant C57BL/6 (IL-10(-/-)) and control (IL-10(+/+)) mice were administered LPS on day 17 of pregnancy, the dose of LPS required to elicit 50% preterm fetal loss was 10-fold lower in IL-10(-/-) mice than in IL-10(+/+) mice. Surviving fetuses in IL-10(-/-) mice exhibited fetal growth restriction at lower doses of LPS than IL-10(+/+) mice. Marked elevation of LPS-induced immunoactive TNF-alpha and IL-6 was evident in the serum, uterus, and placenta of IL-10(-/-) mice, and TNF-alpha and IL-6 mRNA expression was elevated in the uterus and placenta, but not the fetus. Serum IL-1alpha, IFN-gamma, and IL-12p40 were increased and soluble TNFRII was diminished in the absence of IL-10, with these changes also reflected in the gestational tissues. Administration of rIL-10 to IL-10(-/-) mice attenuated proinflammatory cytokine synthesis and alleviated their increased susceptibility to preterm loss. Exogenous IL-10 also protected IL-10(+/+) mice from fetal loss. These data show that IL-10 modulates resistance to inflammatory stimuli by down-regulating proinflammatory cytokines in the uterus and placenta. Abundance of endogenous IL-10 in gestational tissues is therefore identified as a critical determinant of resistance to preterm labor, and IL-10 may provide a useful therapeutic agent in this common condition.     

Accelerated prion disease in the absence of interleukin-10

The identity of pro- and anti-inflammatory cytokines in the neuropathogenesis of prion diseases remains undefined. Here we have investigated the role of anti-inflammatory cytokines on the progression of prion disease through the use of mice that lack interleukin-4 (IL-4), IL-10, IL-13, or both IL-4 and IL-13. Collectively our data show that among these anti-inflammatory cytokines, IL-10 plays a prominent role in the regulation of prion disease. Mice deficient in IL-10 are highly susceptible to the development of prion disease and show a markedly shortened incubation time. In addition, we have correlated cytokine gene expression in prion-inoculated IL-10(-/-) mice to wild-type-inoculated animals. Our experiments show that in the absence of IL-10 there is an early expression of tumor necrosis factor alpha (TNF-alpha). In wild-type prion-inoculated mice, the expression of TNF-alpha mRNA occurs at a later time point that correlates with the extended incubation time for terminal disease development in these animals compared to those that lack IL-10. Elevated levels of IL-13 mRNA are found at early time points in the central nervous system of prion-inoculated IL-10(-/-) mice. At terminal disease, the brains of wild-type mice inoculated with RML or ME7 are characterized by elevated levels of mRNA for the proinflammatory cytokines TNF-alpha and IL-1beta, together with the anti-inflammatory cytokines IL-10, IL-13, and transforming growth factor beta. Our data are consistent with a role for proinflammatory cytokines in the initiation of pathology during prion disease and an attempt by anti-inflammatory cytokines to regulate the ensuing, invariably fatal pathology.     

IL-8 in septic shock, endotoxemia, and after IL-1 administration

Much effort has been directed toward elucidating the host response to sepsis and inflammation, resulting in the definition of a cascade of endogenous mediators that direct metabolic and immunological responses. Here we report that IL-8, a novel cytokine produced by a variety of cells in vitro in response to stimulation with bacterial LPS and the proinflammatory cytokines, appears in the circulation of primates in vivo during septic shock, sublethal endotoxemia, and after the administration of IL-1 alpha. The magnitude of the IL-8 response correlates with the severity of the insult, and levels of IL-8 peak relatively late, after those of TNF-alpha and IL-1 beta, and simultaneously with those of IL-6. IL-8 has been primarily defined as a selective activator and chemoattractant of neutrophils, and we demonstrate that after LPS or IL-1 alpha infusion, circulating neutrophil numbers rapidly recover from an initial neutropenia while IL-8 concentrations are maximal, supporting the hypothesis that IL-8 influences circulating leukocyte populations in vivo. We conclude that IL-8 is another participant in the cytokine cascade elicited by sepsis and inflammation and, as such, may play a significant role in host defense and disease.     

Inflammatory cytokines IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha impart neuroprotection to an excitotoxin through distinct pathways.

The proinflammatory cytokines IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha are produced within the CNS, and, similar to the periphery, they have pleotrophic and overlapping functions. We have shown previously that TNF-alpha increases neuronal survival to a toxic influx of calcium mediated through neuronal N-methyl-d -aspartic acid (NMDA) glutamate-gated ion channels. This process, termed excitotoxicity, is a major contributor to neuronal death following ischemia or stroke. Neuroprotection by this cytokine requires both activation of the p55/TNF receptor type I and the release of TNF-alpha from neurons, and it is inhibited by the plant alkaloid nicotine. Here, we report that other inflammatory cytokines (IL-1 alpha, IL-1 beta, and IL-6) are also neuroprotective to excessive NMDA challenge in our system. Neuroprotection provided by IL-1 is distinct from TNF-alpha because it is inhibited by IL-1 receptor antagonist; it is not antagonized by nicotine, but it is inhibited by a neutralizing Ab to nerve growth factor (NGF). Similar to IL-1, IL-6-mediated neuroprotection is also antagonized by pretreatment with IL-1 receptor antagonist and it is not affected by nicotine. However, neutralizing anti-NGF only partially blocks IL-6-mediated protection. These studies support an important role for distinct but overlapping neuroprotective cytokine effects in the CNS.     

Apolipoprotein E knock-out mice are highly susceptible to endotoxemia and Klebsiella pneumoniae infection

Lipoproteins are able to neutralize bacterial lipopolysaccharide (LPS) and thereby inhibit the proinflammatory cytokine response. In a previous study, we demonstrated that hypercholesterolemic low density lipoprotein receptor knock-out (LDLr-/-) mice are protected against lethal endotoxemia and gram-negative infection. In the present study we investigated the susceptibility of apolipoprotein E knock-out mice (apoE-/-) to LPS and to Klebsiella pneumoniae. These mice have increased plasma lipoprotein concentrations in the very low density lipoprotein (VLDL)-sized fraction. Despite 8 -fold higher plasma cholesterol levels compared to controls, and in contrast to LDLr-/- mice, apoE-/- mice were significantly more susceptible to endotoxemia and to K. pneumoniae infection. Circulating TNFalpha concentrations after intravenously injected LPS were 4 - to 5-fold higher in apoE-/- mice, whereas IL-1alpha, IL-1beta, and IL-6 did not differ. This TNF response was not due to an increased cytokine production capacity of cells from apoE-/- mice, as ex vivo cytokine production in response to LPS did not differ between apoE-/- and control mice. The LPS-neutralizing capacity of apoE-/- plasma was significantly less than that of controls. Most likely, the absence of apoE itself in the knock-out mice explains the failure to neutralize LPS, despite the very high cholesterol concentrations.     

Evidence for IFN-gamma as a mediator of the lethality of endotoxin and tumor necrosis factor-alpha.

Current evidence indicates that endogenously produced peptide cytokines, most notably TNF-alpha and IL-1, mediate the lethality of experimental endotoxemia. Because circulating serum levels of IFN-gamma can be detected soon after TNF-alpha and IL-1 in response to endotoxin, we investigated the role of IFN-gamma in endotoxin and TNF-alpha lethality. Specific neutralizing antibodies to murine TNF-alpha (anti-TNF-alpha Ab) or murine IFN gamma (anti-IFN-gamma Ab) produced in our laboratory protected mice against the lethality of Escherichia coli endotoxin (LPS) administered 6 h later. Serum IFN-gamma levels 2 h after i.v. LPS were lower in mice treated with anti-TNF-alpha Ab compared to mice that received nonimmune IgG (median less than 2.5 vs 3.0 U/ml, P2 less than 0.05). In contrast, serum TNF-alpha levels 1 h after i.v. LPS peaked more than fourfold higher in mice treated with anti-IFN-gamma Ab compared to controls (median greater than 6400 vs 1405 pg/ml, p2 less than 0.05). Doses of TNF-alpha (300 micrograms/kg) and IFN-gamma (50,000 U) which were well tolerated when given individually were synergistically lethal in combination (0% lethality vs 100% lethality, P2 less than 0.001), and were associated with higher serum levels of IL-6 than with either cytokine alone. Anti-IFN-gamma Ab provided complete protection against exogenous human rTNF-alpha at the LD100 dose (1400 micrograms/kg, p2 less than 0.001), and in fact prevented lethality at doses four- to fivefold greater than the LD100 human rTNF-alpha (up to 6000 micrograms/kg). We conclude that IFN-gamma is synergistic with TNF-alpha, is essential for the lethality of LPS and TNF-alpha, and may have modulating effects on the negative control of serum levels of TNF-alpha after LPS in mice.     

Endotoxin and Staphylococcus aureus enterotoxin A induce different patterns of cytokines.

The effects of Staphylococcus aureus enterotoxin A (SEA) and lipopolysaccharide (LPS) in cytokine production were assessed at the single cell level in cells obtained from healthy blood donors. Cytokine production was studied with UV-microscopy of fixed and permeabilized cells stained with cytokine specific monoclonal antibodies. The cytokines evaluated included tumour necrosis factor (TNF)-alpha, interleukin (IL)-1 alpha, IL-1 beta, IL-6, IL-8, IL-10, IL-2, IL-4, interferon (IFN)-gamma and TNF-beta. LPS exhibited marked production of IL-1 alpha, IL-1 beta, TNF-alpha, IL-6 and IL-8. After LPS stimulation IL-1 alpha, IL-1 beta, TNF-alpha and IL-8 were the dominating products, all peaking at or before 4 hours after cell stimulation. In addition, IL-10 production was evident after 12 hours of cell stimulation. The T-lymphocyte-derived cytokines TNF-beta, IL-2, IFN-gamma and IL-4 were never detected in the cultures. All cytokine production, except IL-8, was downregulated at 96 hours. In contrast, peak production of IL-1 alpha, IL-1 beta and IL-8, which were the dominant products, occurred after 12 hours in the SEA-stimulated cultures. Further, a significant T-lymphocyte production of TNF-beta, TNF-alpha, IFN-gamma and IL-2 was found with peak production 12-48 hours after initiation. Only low amounts of IL-6 were evident. The two types of cytokine pattern and kinetics found may correspond to the different clinical conditions after invasive Gram-negative Escherichia coli vs Gram-positive Staphylococcus aureus infections in humans, with a much more rapid onset of disease after E. coli infections.(ABSTRACT TRUNCATED AT 250 WORDS)