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Tregs Modulate Lymphocyte Proliferation, Activation, and Resident-Memory T-Cell Accumulation within the Brain during MCMV Infection.

Prasad S, Hu S, Sheng WS, Singh A, Lokensgard JR - PLoS ONE (2015)

Bottom Line: Furthermore, at 30 dpi we found the majority of CD8+ T-cells were CD127hi KLRG1- indicating that the cells were long lived memory precursor cells.These cells showed marked elevation of CD103 expression, a marker of tissue resident-memory T-cells (TRM) in the CNS, in untreated animals when compared to DTx-treated animals suggesting that generation of TRM is impaired upon Treg depletion.Moreover, the effector function of TRM as indicated by granzyme B production in response to peptide re-stimulation was found to be more potent in Treg-sufficient animals.

View Article: PubMed Central - PubMed

Affiliation: Neuroimmunology Laboratory, Center for Infectious Diseases and Microbiology Translational Research, Department of Medicine, University of Minnesota, Minneapolis, Minnesota, 55455, United States of America.

ABSTRACT
Accumulation and retention of regulatory T-cells (Tregs) has been reported within post viral-encephalitic brains, however, the full extent to which these cells modulate neuroinflammation is yet to be elucidated. Here, we used Foxp3-DTR (diphtheria toxin receptor) knock-in transgenic mice, which upon administration of low dose diphtheria toxin (DTx) results in specific deletion of Tregs. We investigated the proliferation status of various immune cell subtypes within inflamed central nervous system (CNS) tissue. Depletion of Tregs resulted in increased proliferation of both CD8+ and CD4+ T-cell subsets within the brain at 14 d post infection (dpi) when compared to Treg-sufficient animals. At 30 dpi, while proliferation of CD8+ T-cells was controlled within brains of both Treg-depleted and undepleted mice, proliferation of CD4+ T-cells remained significantly enhanced with DTx-treatment. Previous studies have demonstrated that Treg numbers within the brain rebound following DTx treatment to even higher numbers than in untreated animals. Despite this rebound, CD8+ and CD4+ T-cells proliferated at a higher rate when compared to that of Treg-sufficient mice, thus maintaining sustained neuroinflammation. Furthermore, at 30 dpi we found the majority of CD8+ T-cells were CD127hi KLRG1- indicating that the cells were long lived memory precursor cells. These cells showed marked elevation of CD103 expression, a marker of tissue resident-memory T-cells (TRM) in the CNS, in untreated animals when compared to DTx-treated animals suggesting that generation of TRM is impaired upon Treg depletion. Moreover, the effector function of TRM as indicated by granzyme B production in response to peptide re-stimulation was found to be more potent in Treg-sufficient animals. Taken together, our findings demonstrate that Tregs limit neuroinflammatory responses to viral infection by controlling cell proliferation and may direct a larger proportion of lymphocytes within the brain to be maintained as TRM cells.

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Decreased granzyme B production upon antigen re-stimulation by TRM cells from Treg-depleted animals.Single cell suspensions of brain tissue obtained from MCMV-infected mice with and without Treg ablation were re-stimulated using the MCMV-specific peptide M45 (6 h at 37°C). Cells were stained for flow cytometry and granzyme B production was analyzed in CD103+ CD8+ T-cells. (A) Representative plots show expression of granzyme B by CD103-expressing CD8+ T-cells with (+DTx) or without (-DTx) treatment at 30 dpi. (B) Data presented show the percentage of granzyme B production by TRM following peptide stimulation at the indicated time point. **p <0.001 DTx- versus DTx+ MCMV-infected at 30 dpi.
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pone.0145457.g011: Decreased granzyme B production upon antigen re-stimulation by TRM cells from Treg-depleted animals.Single cell suspensions of brain tissue obtained from MCMV-infected mice with and without Treg ablation were re-stimulated using the MCMV-specific peptide M45 (6 h at 37°C). Cells were stained for flow cytometry and granzyme B production was analyzed in CD103+ CD8+ T-cells. (A) Representative plots show expression of granzyme B by CD103-expressing CD8+ T-cells with (+DTx) or without (-DTx) treatment at 30 dpi. (B) Data presented show the percentage of granzyme B production by TRM following peptide stimulation at the indicated time point. **p <0.001 DTx- versus DTx+ MCMV-infected at 30 dpi.

Mentions: TRM cells control reinfection and reactivation of infection because of their ability to produce potent recall responses, proliferate, and generate abundant effector functions to mediate cytotoxicity [16, 39]. We next sought to determine the effect to Treg depletion on granzyme B production, as a measure of potential cytotoxic activity, produced by TRM cells. We assayed granzyme B production following peptide stimulation by brain lymphocytes obtained from DTx-treated and untreated animals at 30 dpi. Strikingly, CD103+CD8+ T-cells from Treg-sufficient animals demonstrated higher levels of granzyme B production when compared to those obtained from animals which lacked Tregs (Fig 11A). This difference was found to be significant: 15.9% of the CD103+CD8+T-cells produced granzyme B in Treg-sufficient animals, compared to 1.69% in Treg-deficient mice P<0.001 (Fig 11B).


Tregs Modulate Lymphocyte Proliferation, Activation, and Resident-Memory T-Cell Accumulation within the Brain during MCMV Infection.

Prasad S, Hu S, Sheng WS, Singh A, Lokensgard JR - PLoS ONE (2015)

Decreased granzyme B production upon antigen re-stimulation by TRM cells from Treg-depleted animals.Single cell suspensions of brain tissue obtained from MCMV-infected mice with and without Treg ablation were re-stimulated using the MCMV-specific peptide M45 (6 h at 37°C). Cells were stained for flow cytometry and granzyme B production was analyzed in CD103+ CD8+ T-cells. (A) Representative plots show expression of granzyme B by CD103-expressing CD8+ T-cells with (+DTx) or without (-DTx) treatment at 30 dpi. (B) Data presented show the percentage of granzyme B production by TRM following peptide stimulation at the indicated time point. **p <0.001 DTx- versus DTx+ MCMV-infected at 30 dpi.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4697843&req=5

pone.0145457.g011: Decreased granzyme B production upon antigen re-stimulation by TRM cells from Treg-depleted animals.Single cell suspensions of brain tissue obtained from MCMV-infected mice with and without Treg ablation were re-stimulated using the MCMV-specific peptide M45 (6 h at 37°C). Cells were stained for flow cytometry and granzyme B production was analyzed in CD103+ CD8+ T-cells. (A) Representative plots show expression of granzyme B by CD103-expressing CD8+ T-cells with (+DTx) or without (-DTx) treatment at 30 dpi. (B) Data presented show the percentage of granzyme B production by TRM following peptide stimulation at the indicated time point. **p <0.001 DTx- versus DTx+ MCMV-infected at 30 dpi.
Mentions: TRM cells control reinfection and reactivation of infection because of their ability to produce potent recall responses, proliferate, and generate abundant effector functions to mediate cytotoxicity [16, 39]. We next sought to determine the effect to Treg depletion on granzyme B production, as a measure of potential cytotoxic activity, produced by TRM cells. We assayed granzyme B production following peptide stimulation by brain lymphocytes obtained from DTx-treated and untreated animals at 30 dpi. Strikingly, CD103+CD8+ T-cells from Treg-sufficient animals demonstrated higher levels of granzyme B production when compared to those obtained from animals which lacked Tregs (Fig 11A). This difference was found to be significant: 15.9% of the CD103+CD8+T-cells produced granzyme B in Treg-sufficient animals, compared to 1.69% in Treg-deficient mice P<0.001 (Fig 11B).

Bottom Line: Furthermore, at 30 dpi we found the majority of CD8+ T-cells were CD127hi KLRG1- indicating that the cells were long lived memory precursor cells.These cells showed marked elevation of CD103 expression, a marker of tissue resident-memory T-cells (TRM) in the CNS, in untreated animals when compared to DTx-treated animals suggesting that generation of TRM is impaired upon Treg depletion.Moreover, the effector function of TRM as indicated by granzyme B production in response to peptide re-stimulation was found to be more potent in Treg-sufficient animals.

View Article: PubMed Central - PubMed

Affiliation: Neuroimmunology Laboratory, Center for Infectious Diseases and Microbiology Translational Research, Department of Medicine, University of Minnesota, Minneapolis, Minnesota, 55455, United States of America.

ABSTRACT
Accumulation and retention of regulatory T-cells (Tregs) has been reported within post viral-encephalitic brains, however, the full extent to which these cells modulate neuroinflammation is yet to be elucidated. Here, we used Foxp3-DTR (diphtheria toxin receptor) knock-in transgenic mice, which upon administration of low dose diphtheria toxin (DTx) results in specific deletion of Tregs. We investigated the proliferation status of various immune cell subtypes within inflamed central nervous system (CNS) tissue. Depletion of Tregs resulted in increased proliferation of both CD8+ and CD4+ T-cell subsets within the brain at 14 d post infection (dpi) when compared to Treg-sufficient animals. At 30 dpi, while proliferation of CD8+ T-cells was controlled within brains of both Treg-depleted and undepleted mice, proliferation of CD4+ T-cells remained significantly enhanced with DTx-treatment. Previous studies have demonstrated that Treg numbers within the brain rebound following DTx treatment to even higher numbers than in untreated animals. Despite this rebound, CD8+ and CD4+ T-cells proliferated at a higher rate when compared to that of Treg-sufficient mice, thus maintaining sustained neuroinflammation. Furthermore, at 30 dpi we found the majority of CD8+ T-cells were CD127hi KLRG1- indicating that the cells were long lived memory precursor cells. These cells showed marked elevation of CD103 expression, a marker of tissue resident-memory T-cells (TRM) in the CNS, in untreated animals when compared to DTx-treated animals suggesting that generation of TRM is impaired upon Treg depletion. Moreover, the effector function of TRM as indicated by granzyme B production in response to peptide re-stimulation was found to be more potent in Treg-sufficient animals. Taken together, our findings demonstrate that Tregs limit neuroinflammatory responses to viral infection by controlling cell proliferation and may direct a larger proportion of lymphocytes within the brain to be maintained as TRM cells.

Show MeSH
Related in: MedlinePlus