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Cholera toxin suppresses interleukin (IL)-12 production and IL-12 receptor beta1 and beta2 chain expression.

Braun MC, He J, Wu CY, Kelsall BL - J. Exp. Med. (1999)

Bottom Line: This suppression occurred at the level of gene transcription, was maximal at low concentrations of CT, and was dependent on the A subunit of the toxin, since purified CT B subunit had minimal effect.The effects of CT were not due to autocrine production of IL-10, TGF-beta1, or prostaglandin E2.In vivo, mice given CT before systemic challenge with lipopolysaccharide had markedly reduced serum levels of IL-12 p40 and interferon gamma.

View Article: PubMed Central - PubMed

Affiliation: Immune Cell Interaction Unit, Mucosal Immunity Section, National Institutes of Allergy and Infectious Disease, National Institutes of Health, Bethesda, Maryland 20892, USA.

ABSTRACT
Cholera toxin (CT) is a potent mucosal vaccine adjuvant, which has been shown to induce T helper cell type 2 (Th2) responses in systemic and mucosal tissues. We report that CT inhibits the production of interleukin (IL)-12, a major Th2 counterregulatory cytokine. IL-12 p70 production by stimulated human monocytes was inhibited by CT in a dose-dependent manner. This suppression occurred at the level of gene transcription, was maximal at low concentrations of CT, and was dependent on the A subunit of the toxin, since purified CT B subunit had minimal effect. CT also inhibited the production of IL-12 p70 by monocyte-derived dendritic cells, as well as the production of tumor necrosis factor alpha, but not IL-10, IL-6, or transforming growth factor (TGF)-beta1, by stimulated monocytes. The effects of CT were not due to autocrine production of IL-10, TGF-beta1, or prostaglandin E2. CT inhibited the production of IFN-gamma by anti-CD3-stimulated human peripheral blood mononuclear cell, due in part to suppression of IL-12 production, but also to the inhibition of expression of the beta1 and beta2 chains of the IL-12 receptor on T cells. In vivo, mice given CT before systemic challenge with lipopolysaccharide had markedly reduced serum levels of IL-12 p40 and interferon gamma. These data demonstrate two novel mechanisms by which CT can inhibit Th1 immune responses, and help explain the ability of mucosally administered CT to enhance Th2-dependent immune responses.

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Analysis by reverse  transcription PCR demonstrates  significantly reduced levels of  mRNA for IL-12 p40 and p35,  but not IL-6, in CT-treated cells  after stimulation. mRNA was  obtained at intervals from human  monocytes (107 cells) after stimulation with SAC (0.01%) and  IFN-γ (100 ng/ml) in the presence or absence of CT (10 ng/ml).
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Figure 5: Analysis by reverse transcription PCR demonstrates significantly reduced levels of mRNA for IL-12 p40 and p35, but not IL-6, in CT-treated cells after stimulation. mRNA was obtained at intervals from human monocytes (107 cells) after stimulation with SAC (0.01%) and IFN-γ (100 ng/ml) in the presence or absence of CT (10 ng/ml).

Mentions: We next sought to determine the level at which CT mediates its suppressive effects. For these studies we used semiquantitative reverse transcription PCR to analyze the levels of IL-12 p35 and p40 mRNA present in monocytes stimulated with SAC and IFN-γ in the presence and absence of CT. Stimulation of cells with SAC and IFN-γ resulted in increased mRNA for both p35 and p40, as well as IL-6 (Fig. 5). Pretreatment of monocytes with CT (10 ng/ml) resulted in suppression of SAC and IFN-γ–stimulated mRNA levels for IL-12 p35 and p40, but did not affect levels of mRNA for IL-6. IL-12 p40 and p35 mRNA expression in CT-B–treated (10 ng/ml) monocytes did not differ from SAC and IFN-γ–stimulated controls (Fig. 6). Since previous studies have shown that IL-12 is primarily regulated at the level of transcription (39, 40), the data presented here suggest that CT is acting to suppress IL-12 p70 production by preventing transcription of the genes for both chains of IL-12.


Cholera toxin suppresses interleukin (IL)-12 production and IL-12 receptor beta1 and beta2 chain expression.

Braun MC, He J, Wu CY, Kelsall BL - J. Exp. Med. (1999)

Analysis by reverse  transcription PCR demonstrates  significantly reduced levels of  mRNA for IL-12 p40 and p35,  but not IL-6, in CT-treated cells  after stimulation. mRNA was  obtained at intervals from human  monocytes (107 cells) after stimulation with SAC (0.01%) and  IFN-γ (100 ng/ml) in the presence or absence of CT (10 ng/ml).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2192916&req=5

Figure 5: Analysis by reverse transcription PCR demonstrates significantly reduced levels of mRNA for IL-12 p40 and p35, but not IL-6, in CT-treated cells after stimulation. mRNA was obtained at intervals from human monocytes (107 cells) after stimulation with SAC (0.01%) and IFN-γ (100 ng/ml) in the presence or absence of CT (10 ng/ml).
Mentions: We next sought to determine the level at which CT mediates its suppressive effects. For these studies we used semiquantitative reverse transcription PCR to analyze the levels of IL-12 p35 and p40 mRNA present in monocytes stimulated with SAC and IFN-γ in the presence and absence of CT. Stimulation of cells with SAC and IFN-γ resulted in increased mRNA for both p35 and p40, as well as IL-6 (Fig. 5). Pretreatment of monocytes with CT (10 ng/ml) resulted in suppression of SAC and IFN-γ–stimulated mRNA levels for IL-12 p35 and p40, but did not affect levels of mRNA for IL-6. IL-12 p40 and p35 mRNA expression in CT-B–treated (10 ng/ml) monocytes did not differ from SAC and IFN-γ–stimulated controls (Fig. 6). Since previous studies have shown that IL-12 is primarily regulated at the level of transcription (39, 40), the data presented here suggest that CT is acting to suppress IL-12 p70 production by preventing transcription of the genes for both chains of IL-12.

Bottom Line: This suppression occurred at the level of gene transcription, was maximal at low concentrations of CT, and was dependent on the A subunit of the toxin, since purified CT B subunit had minimal effect.The effects of CT were not due to autocrine production of IL-10, TGF-beta1, or prostaglandin E2.In vivo, mice given CT before systemic challenge with lipopolysaccharide had markedly reduced serum levels of IL-12 p40 and interferon gamma.

View Article: PubMed Central - PubMed

Affiliation: Immune Cell Interaction Unit, Mucosal Immunity Section, National Institutes of Allergy and Infectious Disease, National Institutes of Health, Bethesda, Maryland 20892, USA.

ABSTRACT
Cholera toxin (CT) is a potent mucosal vaccine adjuvant, which has been shown to induce T helper cell type 2 (Th2) responses in systemic and mucosal tissues. We report that CT inhibits the production of interleukin (IL)-12, a major Th2 counterregulatory cytokine. IL-12 p70 production by stimulated human monocytes was inhibited by CT in a dose-dependent manner. This suppression occurred at the level of gene transcription, was maximal at low concentrations of CT, and was dependent on the A subunit of the toxin, since purified CT B subunit had minimal effect. CT also inhibited the production of IL-12 p70 by monocyte-derived dendritic cells, as well as the production of tumor necrosis factor alpha, but not IL-10, IL-6, or transforming growth factor (TGF)-beta1, by stimulated monocytes. The effects of CT were not due to autocrine production of IL-10, TGF-beta1, or prostaglandin E2. CT inhibited the production of IFN-gamma by anti-CD3-stimulated human peripheral blood mononuclear cell, due in part to suppression of IL-12 production, but also to the inhibition of expression of the beta1 and beta2 chains of the IL-12 receptor on T cells. In vivo, mice given CT before systemic challenge with lipopolysaccharide had markedly reduced serum levels of IL-12 p40 and interferon gamma. These data demonstrate two novel mechanisms by which CT can inhibit Th1 immune responses, and help explain the ability of mucosally administered CT to enhance Th2-dependent immune responses.

Show MeSH
Related in: MedlinePlus