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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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T-cells in vitro proliferation shows no change in the mice with chronic spinal cord injury (SCI). Isolated splenocytes (2 × 105) from uninjured (CT) or T9-SCI mice at chronic phase after injury (SCI) were labeled with CFSE and stimulated ex vivo for three days with anti-CD3+CD28+IL-2 or with IL-2 only. (A) Representative histogram plots show the CFSE fluorescence of CD4+ T-cells and CD8+ T-cells following three-day stimulation with anti-CD3+CD28+IL-2 or with IL-2 only. (B) The line graph shows the percentage of CD4+ T-cells and CD8+ T-cells that have undergone zero to five divisions. Twenty thousand events gated on CD4+ T-cells or CD8+ T-cells were collected. n = 5 mice per group. No statistical difference was detected between the two groups. P > 0.05, two-tailed Student’s t-tests were performed for each cell division number.
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Figure 4: T-cells in vitro proliferation shows no change in the mice with chronic spinal cord injury (SCI). Isolated splenocytes (2 × 105) from uninjured (CT) or T9-SCI mice at chronic phase after injury (SCI) were labeled with CFSE and stimulated ex vivo for three days with anti-CD3+CD28+IL-2 or with IL-2 only. (A) Representative histogram plots show the CFSE fluorescence of CD4+ T-cells and CD8+ T-cells following three-day stimulation with anti-CD3+CD28+IL-2 or with IL-2 only. (B) The line graph shows the percentage of CD4+ T-cells and CD8+ T-cells that have undergone zero to five divisions. Twenty thousand events gated on CD4+ T-cells or CD8+ T-cells were collected. n = 5 mice per group. No statistical difference was detected between the two groups. P > 0.05, two-tailed Student’s t-tests were performed for each cell division number.

Mentions: Since stimulation with anti-CD3/anti-CD28 in presence of IL-2 induces proliferation of T-cells, we also evaluated the proliferative capabilities of these cells isolated from chronically injured mice using CFSE (Figure 4A, B). We did not find any significant difference in the ability of either CD4+ T-cells or CD8+ T-cells to proliferate compared to CT mice.


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)

T-cells in vitro proliferation shows no change in the mice with chronic spinal cord injury (SCI). Isolated splenocytes (2 × 105) from uninjured (CT) or T9-SCI mice at chronic phase after injury (SCI) were labeled with CFSE and stimulated ex vivo for three days with anti-CD3+CD28+IL-2 or with IL-2 only. (A) Representative histogram plots show the CFSE fluorescence of CD4+ T-cells and CD8+ T-cells following three-day stimulation with anti-CD3+CD28+IL-2 or with IL-2 only. (B) The line graph shows the percentage of CD4+ T-cells and CD8+ T-cells that have undergone zero to five divisions. Twenty thousand events gated on CD4+ T-cells or CD8+ T-cells were collected. n = 5 mice per group. No statistical difference was detected between the two groups. P > 0.05, two-tailed Student’s t-tests were performed for each cell division number.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4230802&req=5

Figure 4: T-cells in vitro proliferation shows no change in the mice with chronic spinal cord injury (SCI). Isolated splenocytes (2 × 105) from uninjured (CT) or T9-SCI mice at chronic phase after injury (SCI) were labeled with CFSE and stimulated ex vivo for three days with anti-CD3+CD28+IL-2 or with IL-2 only. (A) Representative histogram plots show the CFSE fluorescence of CD4+ T-cells and CD8+ T-cells following three-day stimulation with anti-CD3+CD28+IL-2 or with IL-2 only. (B) The line graph shows the percentage of CD4+ T-cells and CD8+ T-cells that have undergone zero to five divisions. Twenty thousand events gated on CD4+ T-cells or CD8+ T-cells were collected. n = 5 mice per group. No statistical difference was detected between the two groups. P > 0.05, two-tailed Student’s t-tests were performed for each cell division number.
Mentions: Since stimulation with anti-CD3/anti-CD28 in presence of IL-2 induces proliferation of T-cells, we also evaluated the proliferative capabilities of these cells isolated from chronically injured mice using CFSE (Figure 4A, B). We did not find any significant difference in the ability of either CD4+ T-cells or CD8+ T-cells to proliferate compared to CT mice.

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