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Persistently active microbial molecules prolong innate immune tolerance in vivo.

Lu M, Varley AW, Munford RS - PLoS Pathog. (2013)

Bottom Line: Mice that are unable to inactivate LPS, in contrast, remain tolerant for several months; during this time they respond sluggishly to Gram-negative bacterial challenge, with high mortality.We show here that prolonged macrophage reprogramming is maintained in vivo by the persistence of stimulatory LPS molecules within the cells' in vivo environment, where naïve cells can acquire LPS via cell-cell contact or from the extracellular fluid.Measures that disable microbial molecules might enhance resolution of tissue inflammation and help restore innate defenses in individuals recovering from many different infectious diseases.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America. Lum3@niaid.nih.gov

ABSTRACT
Measures that bolster the resolution phase of infectious diseases may offer new opportunities for improving outcome. Here we show that inactivation of microbial lipopolysaccharides (LPS) can be required for animals to recover from the innate immune tolerance that follows exposure to Gram-negative bacteria. When wildtype mice are exposed to small parenteral doses of LPS or Gram-negative bacteria, their macrophages become reprogrammed (tolerant) for a few days before they resume normal function. Mice that are unable to inactivate LPS, in contrast, remain tolerant for several months; during this time they respond sluggishly to Gram-negative bacterial challenge, with high mortality. We show here that prolonged macrophage reprogramming is maintained in vivo by the persistence of stimulatory LPS molecules within the cells' in vivo environment, where naïve cells can acquire LPS via cell-cell contact or from the extracellular fluid. The findings provide strong evidence that inactivation of a stimulatory microbial molecule can be required for animals to regain immune homeostasis following parenteral exposure to bacteria. Measures that disable microbial molecules might enhance resolution of tissue inflammation and help restore innate defenses in individuals recovering from many different infectious diseases.

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Related in: MedlinePlus

Bioactive LPS in the peritoneum is sufficient to maintain macrophage tolerance in vivo.(A) CD45.1 Aoah+/+ peritoneal cells were transferred to CD45.2 Aoah−/−Tlr4+/+ or Aoah−/−Tlr4−/− mice. Half of the mice in each group received 1 µg LPS i.p. Fourteen days later, the CD45.1 donor macrophages' IL-6 and TNF responses to LPS were determined following ex vivo re-challenge. Naïve Aoah+/+ macrophages became tolerant when they were carried in LPS-injected Aoah−/− mice, whether or not the host mice expressed TLR4. n = 4–7. (B) CD45.2 Aoah−/−Tlr4+/+ or Aoah−/−Tlr4−/− mice received 1 µg LPS i.p. as indicated. Fourteen days later, CD45.1 naïve Aoah+/+ peritoneal cells were transferred i.p. to PBS- or LPS-injected mice. After 24 hours, the responses of the donor macrophages to LPS were measured ex vivo. Exposure to the LPS-containing Aoah−/− peritoneal environment rendered naïve Aoah+/+ macrophages tolerant, whether or not the host mouse was able to respond to the i.p. dose of LPS. Data were combined from 2 experiments. n = 4–6. **, P<0.01; ***, P<0.001. Blue bars, Aoah−/− Tlr4+/+ recipients; light blue bars, Aoah−/−Tlr4−/− recipients; diagonal markings represent i.p. LPS injection.
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ppat-1003339-g004: Bioactive LPS in the peritoneum is sufficient to maintain macrophage tolerance in vivo.(A) CD45.1 Aoah+/+ peritoneal cells were transferred to CD45.2 Aoah−/−Tlr4+/+ or Aoah−/−Tlr4−/− mice. Half of the mice in each group received 1 µg LPS i.p. Fourteen days later, the CD45.1 donor macrophages' IL-6 and TNF responses to LPS were determined following ex vivo re-challenge. Naïve Aoah+/+ macrophages became tolerant when they were carried in LPS-injected Aoah−/− mice, whether or not the host mice expressed TLR4. n = 4–7. (B) CD45.2 Aoah−/−Tlr4+/+ or Aoah−/−Tlr4−/− mice received 1 µg LPS i.p. as indicated. Fourteen days later, CD45.1 naïve Aoah+/+ peritoneal cells were transferred i.p. to PBS- or LPS-injected mice. After 24 hours, the responses of the donor macrophages to LPS were measured ex vivo. Exposure to the LPS-containing Aoah−/− peritoneal environment rendered naïve Aoah+/+ macrophages tolerant, whether or not the host mouse was able to respond to the i.p. dose of LPS. Data were combined from 2 experiments. n = 4–6. **, P<0.01; ***, P<0.001. Blue bars, Aoah−/− Tlr4+/+ recipients; light blue bars, Aoah−/−Tlr4−/− recipients; diagonal markings represent i.p. LPS injection.

Mentions: We then asked how the peritoneal environment determines the fate of macrophages. Although bioactive LPS might still be present in the peritoneum, LPS also induces a broad array of inflammatory mediators, some of which (e.g., IL-10, TGF-β, IL-1 receptor antagonist) may promote macrophage reprogramming [15]. To find out whether wildtype macrophages can become tolerant in an Aoah−/− environment that lacks LPS-induced mediators, we transferred Aoah+/+ CD45.1 peritoneal cells into mice that lack both AOAH and TLR4 (Aoah−/−Tlr4−/− CD45.2) and can neither deacylate, nor respond to, LPS. Fourteen days after i.p. LPS injection, the donor Aoah+/+ CD45.1 macrophages were tolerant (Fig. 4A); since the recipient mice do not produce LPS-induced mediators, this observation suggested strongly that such mediators are not required to maintain prolonged tolerance in vivo. In another approach, CD45.2 Aoah−/−Tlr4+/+ or Aoah−/−Tlr4−/− mice were given LPS i.p. Fourteen days later, CD45.1 naïve Aoah+/+ peritoneal cells were introduced into the peritoneal cavity. One day after transfer, the donor macrophages had become tolerant in both Aoah−/−Tlr4+/+ and Aoah−/−Tlr4−/− recipients (Fig. 4B). These findings suggested that bioactive LPS is present for a prolonged period in the LPS-exposed Aoah−/− peritoneum and that this LPS can induce and maintain macrophage tolerance in the absence of LPS-induced host mediators.


Persistently active microbial molecules prolong innate immune tolerance in vivo.

Lu M, Varley AW, Munford RS - PLoS Pathog. (2013)

Bioactive LPS in the peritoneum is sufficient to maintain macrophage tolerance in vivo.(A) CD45.1 Aoah+/+ peritoneal cells were transferred to CD45.2 Aoah−/−Tlr4+/+ or Aoah−/−Tlr4−/− mice. Half of the mice in each group received 1 µg LPS i.p. Fourteen days later, the CD45.1 donor macrophages' IL-6 and TNF responses to LPS were determined following ex vivo re-challenge. Naïve Aoah+/+ macrophages became tolerant when they were carried in LPS-injected Aoah−/− mice, whether or not the host mice expressed TLR4. n = 4–7. (B) CD45.2 Aoah−/−Tlr4+/+ or Aoah−/−Tlr4−/− mice received 1 µg LPS i.p. as indicated. Fourteen days later, CD45.1 naïve Aoah+/+ peritoneal cells were transferred i.p. to PBS- or LPS-injected mice. After 24 hours, the responses of the donor macrophages to LPS were measured ex vivo. Exposure to the LPS-containing Aoah−/− peritoneal environment rendered naïve Aoah+/+ macrophages tolerant, whether or not the host mouse was able to respond to the i.p. dose of LPS. Data were combined from 2 experiments. n = 4–6. **, P<0.01; ***, P<0.001. Blue bars, Aoah−/− Tlr4+/+ recipients; light blue bars, Aoah−/−Tlr4−/− recipients; diagonal markings represent i.p. LPS injection.
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Related In: Results  -  Collection

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ppat-1003339-g004: Bioactive LPS in the peritoneum is sufficient to maintain macrophage tolerance in vivo.(A) CD45.1 Aoah+/+ peritoneal cells were transferred to CD45.2 Aoah−/−Tlr4+/+ or Aoah−/−Tlr4−/− mice. Half of the mice in each group received 1 µg LPS i.p. Fourteen days later, the CD45.1 donor macrophages' IL-6 and TNF responses to LPS were determined following ex vivo re-challenge. Naïve Aoah+/+ macrophages became tolerant when they were carried in LPS-injected Aoah−/− mice, whether or not the host mice expressed TLR4. n = 4–7. (B) CD45.2 Aoah−/−Tlr4+/+ or Aoah−/−Tlr4−/− mice received 1 µg LPS i.p. as indicated. Fourteen days later, CD45.1 naïve Aoah+/+ peritoneal cells were transferred i.p. to PBS- or LPS-injected mice. After 24 hours, the responses of the donor macrophages to LPS were measured ex vivo. Exposure to the LPS-containing Aoah−/− peritoneal environment rendered naïve Aoah+/+ macrophages tolerant, whether or not the host mouse was able to respond to the i.p. dose of LPS. Data were combined from 2 experiments. n = 4–6. **, P<0.01; ***, P<0.001. Blue bars, Aoah−/− Tlr4+/+ recipients; light blue bars, Aoah−/−Tlr4−/− recipients; diagonal markings represent i.p. LPS injection.
Mentions: We then asked how the peritoneal environment determines the fate of macrophages. Although bioactive LPS might still be present in the peritoneum, LPS also induces a broad array of inflammatory mediators, some of which (e.g., IL-10, TGF-β, IL-1 receptor antagonist) may promote macrophage reprogramming [15]. To find out whether wildtype macrophages can become tolerant in an Aoah−/− environment that lacks LPS-induced mediators, we transferred Aoah+/+ CD45.1 peritoneal cells into mice that lack both AOAH and TLR4 (Aoah−/−Tlr4−/− CD45.2) and can neither deacylate, nor respond to, LPS. Fourteen days after i.p. LPS injection, the donor Aoah+/+ CD45.1 macrophages were tolerant (Fig. 4A); since the recipient mice do not produce LPS-induced mediators, this observation suggested strongly that such mediators are not required to maintain prolonged tolerance in vivo. In another approach, CD45.2 Aoah−/−Tlr4+/+ or Aoah−/−Tlr4−/− mice were given LPS i.p. Fourteen days later, CD45.1 naïve Aoah+/+ peritoneal cells were introduced into the peritoneal cavity. One day after transfer, the donor macrophages had become tolerant in both Aoah−/−Tlr4+/+ and Aoah−/−Tlr4−/− recipients (Fig. 4B). These findings suggested that bioactive LPS is present for a prolonged period in the LPS-exposed Aoah−/− peritoneum and that this LPS can induce and maintain macrophage tolerance in the absence of LPS-induced host mediators.

Bottom Line: Mice that are unable to inactivate LPS, in contrast, remain tolerant for several months; during this time they respond sluggishly to Gram-negative bacterial challenge, with high mortality.We show here that prolonged macrophage reprogramming is maintained in vivo by the persistence of stimulatory LPS molecules within the cells' in vivo environment, where naïve cells can acquire LPS via cell-cell contact or from the extracellular fluid.Measures that disable microbial molecules might enhance resolution of tissue inflammation and help restore innate defenses in individuals recovering from many different infectious diseases.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America. Lum3@niaid.nih.gov

ABSTRACT
Measures that bolster the resolution phase of infectious diseases may offer new opportunities for improving outcome. Here we show that inactivation of microbial lipopolysaccharides (LPS) can be required for animals to recover from the innate immune tolerance that follows exposure to Gram-negative bacteria. When wildtype mice are exposed to small parenteral doses of LPS or Gram-negative bacteria, their macrophages become reprogrammed (tolerant) for a few days before they resume normal function. Mice that are unable to inactivate LPS, in contrast, remain tolerant for several months; during this time they respond sluggishly to Gram-negative bacterial challenge, with high mortality. We show here that prolonged macrophage reprogramming is maintained in vivo by the persistence of stimulatory LPS molecules within the cells' in vivo environment, where naïve cells can acquire LPS via cell-cell contact or from the extracellular fluid. The findings provide strong evidence that inactivation of a stimulatory microbial molecule can be required for animals to regain immune homeostasis following parenteral exposure to bacteria. Measures that disable microbial molecules might enhance resolution of tissue inflammation and help restore innate defenses in individuals recovering from many different infectious diseases.

Show MeSH
Related in: MedlinePlus