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Inhibition of allogeneic T cell proliferation by indoleamine 2,3-dioxygenase-expressing dendritic cells: mediation of suppression by tryptophan metabolites.

Terness P, Bauer TM, Röse L, Dufter C, Watzlik A, Simon H, Opelz G - J. Exp. Med. (2002)

Bottom Line: Transgenic DCs decreased the concentration of tryptophan, increased the concentration of kynurenine, the main tryptophan metabolite, and suppressed allogeneic T cell proliferation in vitro.Kynurenine, 3-hydroxykynurenine, and 3-hydroxyanthranilic acid, but no other IDO-induced tryptophan metabolites, suppressed the T cell response, the suppressive effects being additive.Our findings shed light on suppressive mechanisms mediated by DCs and provide an explanation for important biological processes in which IDO activity apparently is increased, such as protection of the fetus from rejection during pregnancy and possibly T cell death in HIV-infected patients.

View Article: PubMed Central - PubMed

Affiliation: Institute of Immunology, Department of Transplantation Immunology, University of Heidelberg, 69120 Heidelberg, Germany. peter_terness@med.uni-heidelberg.de

ABSTRACT
Indoleamine 2,3-dioxygenase (IDO), an enzyme involved in the catabolism of tryptophan, is expressed in certain cells and tissues, particularly in antigen-presenting cells of lymphoid organs and in the placenta. It was shown that IDO prevents rejection of the fetus during pregnancy, probably by inhibiting alloreactive T cells, and it was suggested that IDO-expression in antigen-presenting cells may control autoreactive immune responses. Degradation of tryptophan, an essential amino acid required for cell proliferation, was reported to be the mechanism of IDO-induced T cell suppression. Because we wanted to study the action of IDO-expressing dendritic cells (DCs) on allogeneic T cells, the human IDO gene was inserted into an adenoviral vector and expressed in DCs. Transgenic DCs decreased the concentration of tryptophan, increased the concentration of kynurenine, the main tryptophan metabolite, and suppressed allogeneic T cell proliferation in vitro. Kynurenine, 3-hydroxykynurenine, and 3-hydroxyanthranilic acid, but no other IDO-induced tryptophan metabolites, suppressed the T cell response, the suppressive effects being additive. T cells, once stopped in their proliferation, could not be restimulated. Inhibition of proliferation was likely due to T cell death because suppressive tryptophan catabolites exerted a cytotoxic action on CD3(+) cells. This action preferentially affected activated T cells and increased gradually with exposure time. In addition to T cells, B and natural killer (NK) cells were also killed, whereas DCs were not affected. Our findings shed light on suppressive mechanisms mediated by DCs and provide an explanation for important biological processes in which IDO activity apparently is increased, such as protection of the fetus from rejection during pregnancy and possibly T cell death in HIV-infected patients.

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Time dependency of cytotoxicity and preferential killing of activated T cells. T cells were separated from PBMCs using magnetic beads and kept in culture (A) with anti-CD3 antibody or (B) without anti-CD3 antibody, in the presence of a mixture of tryptophan metabolites (kynurenine plus 3-hydroxykynurenine plus anthranilic acid plus 3-hydroxyanthranilic acid plus quinolinic acid) (concentrations: 0, 8, 16, 32 μM for each compound). The percentage of dead cells (ordinate) was measured every day (abscissa) by 7-AAD staining.
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fig10: Time dependency of cytotoxicity and preferential killing of activated T cells. T cells were separated from PBMCs using magnetic beads and kept in culture (A) with anti-CD3 antibody or (B) without anti-CD3 antibody, in the presence of a mixture of tryptophan metabolites (kynurenine plus 3-hydroxykynurenine plus anthranilic acid plus 3-hydroxyanthranilic acid plus quinolinic acid) (concentrations: 0, 8, 16, 32 μM for each compound). The percentage of dead cells (ordinate) was measured every day (abscissa) by 7-AAD staining.

Mentions: In a second experiment we addressed the question whether T cells stimulated with allogeneic DCs in the presence of kynurenine can be restimulated with donor-specific or third party DCs (Fig. 6) . As expected, T cells directed against a certain donor, once suppressed cannot be restimulated with DCs from the same donor (Fig. 6, top and bottom curve at 1,500, 751, and 375 μM). Third-party DCs, however, are able to restimulate the T cells (medium curve). The degree of restimulation by third-party donors depends on the dose of kynurenine to which the cells were exposed. At extremely high doses (1,500 or 750 μM) only minimal reactions was noted, whereas at medium or low doses (375–47 μM) significant restimulation takes place. Most importantly, at any kynurenine concentration, third-party restimulation (medium curve) was significantly higher than donor-specific restimulation (bottom curve). This finding suggests that kynurenine preferentially compromises activated T cells. As we will see later (Fig. 10, A and B) , this was confirmed by further analyses.


Inhibition of allogeneic T cell proliferation by indoleamine 2,3-dioxygenase-expressing dendritic cells: mediation of suppression by tryptophan metabolites.

Terness P, Bauer TM, Röse L, Dufter C, Watzlik A, Simon H, Opelz G - J. Exp. Med. (2002)

Time dependency of cytotoxicity and preferential killing of activated T cells. T cells were separated from PBMCs using magnetic beads and kept in culture (A) with anti-CD3 antibody or (B) without anti-CD3 antibody, in the presence of a mixture of tryptophan metabolites (kynurenine plus 3-hydroxykynurenine plus anthranilic acid plus 3-hydroxyanthranilic acid plus quinolinic acid) (concentrations: 0, 8, 16, 32 μM for each compound). The percentage of dead cells (ordinate) was measured every day (abscissa) by 7-AAD staining.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196057&req=5

fig10: Time dependency of cytotoxicity and preferential killing of activated T cells. T cells were separated from PBMCs using magnetic beads and kept in culture (A) with anti-CD3 antibody or (B) without anti-CD3 antibody, in the presence of a mixture of tryptophan metabolites (kynurenine plus 3-hydroxykynurenine plus anthranilic acid plus 3-hydroxyanthranilic acid plus quinolinic acid) (concentrations: 0, 8, 16, 32 μM for each compound). The percentage of dead cells (ordinate) was measured every day (abscissa) by 7-AAD staining.
Mentions: In a second experiment we addressed the question whether T cells stimulated with allogeneic DCs in the presence of kynurenine can be restimulated with donor-specific or third party DCs (Fig. 6) . As expected, T cells directed against a certain donor, once suppressed cannot be restimulated with DCs from the same donor (Fig. 6, top and bottom curve at 1,500, 751, and 375 μM). Third-party DCs, however, are able to restimulate the T cells (medium curve). The degree of restimulation by third-party donors depends on the dose of kynurenine to which the cells were exposed. At extremely high doses (1,500 or 750 μM) only minimal reactions was noted, whereas at medium or low doses (375–47 μM) significant restimulation takes place. Most importantly, at any kynurenine concentration, third-party restimulation (medium curve) was significantly higher than donor-specific restimulation (bottom curve). This finding suggests that kynurenine preferentially compromises activated T cells. As we will see later (Fig. 10, A and B) , this was confirmed by further analyses.

Bottom Line: Transgenic DCs decreased the concentration of tryptophan, increased the concentration of kynurenine, the main tryptophan metabolite, and suppressed allogeneic T cell proliferation in vitro.Kynurenine, 3-hydroxykynurenine, and 3-hydroxyanthranilic acid, but no other IDO-induced tryptophan metabolites, suppressed the T cell response, the suppressive effects being additive.Our findings shed light on suppressive mechanisms mediated by DCs and provide an explanation for important biological processes in which IDO activity apparently is increased, such as protection of the fetus from rejection during pregnancy and possibly T cell death in HIV-infected patients.

View Article: PubMed Central - PubMed

Affiliation: Institute of Immunology, Department of Transplantation Immunology, University of Heidelberg, 69120 Heidelberg, Germany. peter_terness@med.uni-heidelberg.de

ABSTRACT
Indoleamine 2,3-dioxygenase (IDO), an enzyme involved in the catabolism of tryptophan, is expressed in certain cells and tissues, particularly in antigen-presenting cells of lymphoid organs and in the placenta. It was shown that IDO prevents rejection of the fetus during pregnancy, probably by inhibiting alloreactive T cells, and it was suggested that IDO-expression in antigen-presenting cells may control autoreactive immune responses. Degradation of tryptophan, an essential amino acid required for cell proliferation, was reported to be the mechanism of IDO-induced T cell suppression. Because we wanted to study the action of IDO-expressing dendritic cells (DCs) on allogeneic T cells, the human IDO gene was inserted into an adenoviral vector and expressed in DCs. Transgenic DCs decreased the concentration of tryptophan, increased the concentration of kynurenine, the main tryptophan metabolite, and suppressed allogeneic T cell proliferation in vitro. Kynurenine, 3-hydroxykynurenine, and 3-hydroxyanthranilic acid, but no other IDO-induced tryptophan metabolites, suppressed the T cell response, the suppressive effects being additive. T cells, once stopped in their proliferation, could not be restimulated. Inhibition of proliferation was likely due to T cell death because suppressive tryptophan catabolites exerted a cytotoxic action on CD3(+) cells. This action preferentially affected activated T cells and increased gradually with exposure time. In addition to T cells, B and natural killer (NK) cells were also killed, whereas DCs were not affected. Our findings shed light on suppressive mechanisms mediated by DCs and provide an explanation for important biological processes in which IDO activity apparently is increased, such as protection of the fetus from rejection during pregnancy and possibly T cell death in HIV-infected patients.

Show MeSH
Related in: MedlinePlus