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Chronic thoracic spinal cord injury impairs CD8+ T-cell function by up-regulating programmed cell death-1 expression.

Zha J, Smith A, Andreansky S, Bracchi-Ricard V, Bethea JR - J Neuroinflammation (2014)

Bottom Line: Chronic SCI impaired both CD4+ and CD8+ T-cell cytokine production.The observed T-cell dysfunction correlated with increased expression of programmed cell death 1 (PD-1) exhaustion marker on these cells.Blocking PD-1 signaling in vitro restored the CD8+ T-cell functional defect.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Miami Project to Cure Paralysis, Department of Neurosurgery, Miller School of Medicine, University of Miami, Miami, FL 33136, USA. VBracchi@med.miami.edu.

ABSTRACT

Background: Chronic spinal cord injury (SCI) induces immune depression in patients, which contributes to their higher risk of developing infections. While defects in humoral immunity have been reported, complications in T-cell immunity during the chronic phase of SCI have not yet been explored.

Methods: To assess the impact of chronic SCI on peripheral T-cell number and function we used a mouse model of severe spinal cord contusion at thoracic level T9 and performed flow cytometry analysis on the spleen for T-cell markers along with intracellular cytokine staining. Furthermore we identified alterations in sympathetic activity in the spleen of chronic SCI mice by measuring splenic levels of tyrosine hydroxylase (TH) and norepinephrine (NE). To gain insight into the neurogenic mechanism leading to T-cell dysfunction we performed in vitro NE stimulation of T-cells followed by flow cytometry analysis for T-cell exhaustion marker.

Results: Chronic SCI impaired both CD4+ and CD8+ T-cell cytokine production. The observed T-cell dysfunction correlated with increased expression of programmed cell death 1 (PD-1) exhaustion marker on these cells. Blocking PD-1 signaling in vitro restored the CD8+ T-cell functional defect. In addition, we showed that chronic SCI mice had higher levels of splenic NE, which contributed to the T-cell exhaustion phenotype, as PD-1 expression on both CD4+ and CD8+ T-cells was up-regulated following sustained exposure to NE in vitro.

Conclusions: These studies indicate that alteration of sympathetic activity following chronic SCI induces CD8+ T-cell exhaustion, which in turn impairs T-cell function and contributes to immune depression. Inhibition of the exhaustion pathway should be considered as a new therapeutic strategy for chronic SCI-induced immune depression.

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Up regulation of PD-l ligand PD-L1 expression on splenic B-cells and macrophages following chronic spinal cord injury (SCI). (A) Representative histogram plots show PD-L1 expression on gated B220+ B-cells, CD11b+ macrophages and CD11c+ dendritic cells from uninjured (CT) and T9-SCI mice at chronic phase after injury (SCI). (B) Bar graphs show the mean ± SEM of PD-L1 mean fluorescence intensities (MFI) in gated B-cells, macrophages and dendritic cells from CT and SCI mice. Ten thousand events gated on live singlets were collected. n = 4 mice per group. *P < 0.05, **P < 0.01, one-tailed Student’s t-test.
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Figure 6: Up regulation of PD-l ligand PD-L1 expression on splenic B-cells and macrophages following chronic spinal cord injury (SCI). (A) Representative histogram plots show PD-L1 expression on gated B220+ B-cells, CD11b+ macrophages and CD11c+ dendritic cells from uninjured (CT) and T9-SCI mice at chronic phase after injury (SCI). (B) Bar graphs show the mean ± SEM of PD-L1 mean fluorescence intensities (MFI) in gated B-cells, macrophages and dendritic cells from CT and SCI mice. Ten thousand events gated on live singlets were collected. n = 4 mice per group. *P < 0.05, **P < 0.01, one-tailed Student’s t-test.

Mentions: We sought to determine whether the ligand for PD-1 receptor (PD-L1) was up-regulated following chronic SCI, as engagement of PD-1 ligand with PD-1 induces T-cell exhaustion signaling. We measured the expression of PD-L1 on B-cells, macrophages and dendritic cells. Compared with CT group, the mean fluorescence intensity (MFI) values for PD-L1 were significantly increased on splenic B-cells (uninjured: 1,169 ± 38; chronic SCI: 1,451 ± 54; P = 0.003) and macrophages (uninjured: 1213 ± 34; chronic SCI: 2061 ± 270; P = 0.03) from the chronic SCI group (Figure 6A, B). However, PD-L1 expression on dendritic cells was similar between CT and SCI groups (uninjured: 3,074 ± 241; chronic SCI: 3,468 ± 202; P = 0.13) (Figure 6A, B).


Chronic thoracic spinal cord injury impairs CD8+ T-cell function by up-regulating programmed cell death-1 expression.

Zha J, Smith A, Andreansky S, Bracchi-Ricard V, Bethea JR - J Neuroinflammation (2014)

Up regulation of PD-l ligand PD-L1 expression on splenic B-cells and macrophages following chronic spinal cord injury (SCI). (A) Representative histogram plots show PD-L1 expression on gated B220+ B-cells, CD11b+ macrophages and CD11c+ dendritic cells from uninjured (CT) and T9-SCI mice at chronic phase after injury (SCI). (B) Bar graphs show the mean ± SEM of PD-L1 mean fluorescence intensities (MFI) in gated B-cells, macrophages and dendritic cells from CT and SCI mice. Ten thousand events gated on live singlets were collected. n = 4 mice per group. *P < 0.05, **P < 0.01, one-tailed Student’s t-test.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4230802&req=5

Figure 6: Up regulation of PD-l ligand PD-L1 expression on splenic B-cells and macrophages following chronic spinal cord injury (SCI). (A) Representative histogram plots show PD-L1 expression on gated B220+ B-cells, CD11b+ macrophages and CD11c+ dendritic cells from uninjured (CT) and T9-SCI mice at chronic phase after injury (SCI). (B) Bar graphs show the mean ± SEM of PD-L1 mean fluorescence intensities (MFI) in gated B-cells, macrophages and dendritic cells from CT and SCI mice. Ten thousand events gated on live singlets were collected. n = 4 mice per group. *P < 0.05, **P < 0.01, one-tailed Student’s t-test.
Mentions: We sought to determine whether the ligand for PD-1 receptor (PD-L1) was up-regulated following chronic SCI, as engagement of PD-1 ligand with PD-1 induces T-cell exhaustion signaling. We measured the expression of PD-L1 on B-cells, macrophages and dendritic cells. Compared with CT group, the mean fluorescence intensity (MFI) values for PD-L1 were significantly increased on splenic B-cells (uninjured: 1,169 ± 38; chronic SCI: 1,451 ± 54; P = 0.003) and macrophages (uninjured: 1213 ± 34; chronic SCI: 2061 ± 270; P = 0.03) from the chronic SCI group (Figure 6A, B). However, PD-L1 expression on dendritic cells was similar between CT and SCI groups (uninjured: 3,074 ± 241; chronic SCI: 3,468 ± 202; P = 0.13) (Figure 6A, B).

Bottom Line: Chronic SCI impaired both CD4+ and CD8+ T-cell cytokine production.The observed T-cell dysfunction correlated with increased expression of programmed cell death 1 (PD-1) exhaustion marker on these cells.Blocking PD-1 signaling in vitro restored the CD8+ T-cell functional defect.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Miami Project to Cure Paralysis, Department of Neurosurgery, Miller School of Medicine, University of Miami, Miami, FL 33136, USA. VBracchi@med.miami.edu.

ABSTRACT

Background: Chronic spinal cord injury (SCI) induces immune depression in patients, which contributes to their higher risk of developing infections. While defects in humoral immunity have been reported, complications in T-cell immunity during the chronic phase of SCI have not yet been explored.

Methods: To assess the impact of chronic SCI on peripheral T-cell number and function we used a mouse model of severe spinal cord contusion at thoracic level T9 and performed flow cytometry analysis on the spleen for T-cell markers along with intracellular cytokine staining. Furthermore we identified alterations in sympathetic activity in the spleen of chronic SCI mice by measuring splenic levels of tyrosine hydroxylase (TH) and norepinephrine (NE). To gain insight into the neurogenic mechanism leading to T-cell dysfunction we performed in vitro NE stimulation of T-cells followed by flow cytometry analysis for T-cell exhaustion marker.

Results: Chronic SCI impaired both CD4+ and CD8+ T-cell cytokine production. The observed T-cell dysfunction correlated with increased expression of programmed cell death 1 (PD-1) exhaustion marker on these cells. Blocking PD-1 signaling in vitro restored the CD8+ T-cell functional defect. In addition, we showed that chronic SCI mice had higher levels of splenic NE, which contributed to the T-cell exhaustion phenotype, as PD-1 expression on both CD4+ and CD8+ T-cells was up-regulated following sustained exposure to NE in vitro.

Conclusions: These studies indicate that alteration of sympathetic activity following chronic SCI induces CD8+ T-cell exhaustion, which in turn impairs T-cell function and contributes to immune depression. Inhibition of the exhaustion pathway should be considered as a new therapeutic strategy for chronic SCI-induced immune depression.

Show MeSH
Related in: MedlinePlus