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Genetic absence of PD-1 promotes accumulation of terminally differentiated exhausted CD8+ T cells.

Odorizzi PM, Pauken KE, Paley MA, Sharpe A, Wherry EJ - J. Exp. Med. (2015)

Bottom Line: Increased proliferation between days 8 and 14 postinfection is associated with subsequent decreased CD8(+) T cell survival and disruption of a critical proliferative hierarchy necessary to maintain exhausted populations long term.Ultimately, the absence of PD-1 leads to the accumulation of more cytotoxic, but terminally differentiated, CD8(+) TEX cells.They also highlight a novel role for PD-1 in preserving TEX cell populations from overstimulation, excessive proliferation, and terminal differentiation.

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Affiliation: Department of Microbiology and Penn Institute for Immunology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104 Department of Microbiology and Penn Institute for Immunology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104.

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Reduced survival of PD-1 KO P14 cells during T cell contraction. WT and PD-1 KO P14 cells were mixed at a 1:1 ratio (250 cells each), adoptively transferred into naive recipient mice, and infected with LCMV clone 13. P14 responses were then analyzed at the indicated time points. (A) Percent decrease in the frequency of WT and PD-1 KO P14 cells from peak of T cell response (day 15 p.i.) to chronic phase of infection (day 42 p.i.). Values indicate the mean percent decrease for each population. (B and C) Expression of LIVE/DEAD Aqua (B) and Annexin V (C) as a measure of cell death in WT and PD-1 KO P14 cells at day 18 p.i. in the spleen for individual (histograms) and multiple mice (bar graphs). Values indicate the frequency of P14 cells positive for staining based on FMO staining controls. (D) Expression of CD44 versus FLICA in WT and PD-1 KO P14 cells at day 14 p.i. in the spleen for individual (left) and multiple mice (right). Values indicate the frequency of P14 cells positive for FLICA dye based on FMO staining control. All error bars indicate ±SEM. *, P < 0.05; **, P < 0.01 (paired Student’s t test for B–D and unpaired Student’s t test for A) for all graphs (A–D). All data are representative of three independent experiments with at least four mice per group.
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fig4: Reduced survival of PD-1 KO P14 cells during T cell contraction. WT and PD-1 KO P14 cells were mixed at a 1:1 ratio (250 cells each), adoptively transferred into naive recipient mice, and infected with LCMV clone 13. P14 responses were then analyzed at the indicated time points. (A) Percent decrease in the frequency of WT and PD-1 KO P14 cells from peak of T cell response (day 15 p.i.) to chronic phase of infection (day 42 p.i.). Values indicate the mean percent decrease for each population. (B and C) Expression of LIVE/DEAD Aqua (B) and Annexin V (C) as a measure of cell death in WT and PD-1 KO P14 cells at day 18 p.i. in the spleen for individual (histograms) and multiple mice (bar graphs). Values indicate the frequency of P14 cells positive for staining based on FMO staining controls. (D) Expression of CD44 versus FLICA in WT and PD-1 KO P14 cells at day 14 p.i. in the spleen for individual (left) and multiple mice (right). Values indicate the frequency of P14 cells positive for FLICA dye based on FMO staining control. All error bars indicate ±SEM. *, P < 0.05; **, P < 0.01 (paired Student’s t test for B–D and unpaired Student’s t test for A) for all graphs (A–D). All data are representative of three independent experiments with at least four mice per group.

Mentions: We next examined how the absence of PD-1 affected the transition to later stages of infection. After peak expansion, PD-1 KO P14 cells underwent significantly greater contraction between days 15 and 42 p.i. (88% decrease) compared with WT P14 cells (75% decrease; Fig. 4 A). We hypothesized that this more dramatic contraction was caused by decreased survival in the absence of inhibitory signals from the PD-1 pathway. To test this possibility, WT and PD-1 KO P14 cells were assessed for markers of cell death between days 14 and 20 p.i. in the spleen. A higher frequency of PD-1 KO P14 cells stained with LIVE/DEAD Aqua (Fig. 4 B) and Annexin V (Fig. 4 C), markers of compromised cell membrane integrity which are associated with apoptosis and cell death. PD-1 KO P14 cells also displayed increased staining with fluorescent caspase substrates (FLICA) at day 15 p.i. (Fig. 4 D). In addition, ex vivo survival of PD-1 KO P14 cells was decreased, as demonstrated by a significant reduction in the total frequency of live cells remaining after a 10-h in vitro culture (not depicted). Thus, in the absence of PD-1, virus-specific CD8+ T cells experience considerably more cell death than WT CD8+ T cells of the same specificity in the same inflammatory environment. These findings suggest that PD-1 prevents overstimulation of CD8+ T cells and subsequent excessive cell death during chronic viral infection.


Genetic absence of PD-1 promotes accumulation of terminally differentiated exhausted CD8+ T cells.

Odorizzi PM, Pauken KE, Paley MA, Sharpe A, Wherry EJ - J. Exp. Med. (2015)

Reduced survival of PD-1 KO P14 cells during T cell contraction. WT and PD-1 KO P14 cells were mixed at a 1:1 ratio (250 cells each), adoptively transferred into naive recipient mice, and infected with LCMV clone 13. P14 responses were then analyzed at the indicated time points. (A) Percent decrease in the frequency of WT and PD-1 KO P14 cells from peak of T cell response (day 15 p.i.) to chronic phase of infection (day 42 p.i.). Values indicate the mean percent decrease for each population. (B and C) Expression of LIVE/DEAD Aqua (B) and Annexin V (C) as a measure of cell death in WT and PD-1 KO P14 cells at day 18 p.i. in the spleen for individual (histograms) and multiple mice (bar graphs). Values indicate the frequency of P14 cells positive for staining based on FMO staining controls. (D) Expression of CD44 versus FLICA in WT and PD-1 KO P14 cells at day 14 p.i. in the spleen for individual (left) and multiple mice (right). Values indicate the frequency of P14 cells positive for FLICA dye based on FMO staining control. All error bars indicate ±SEM. *, P < 0.05; **, P < 0.01 (paired Student’s t test for B–D and unpaired Student’s t test for A) for all graphs (A–D). All data are representative of three independent experiments with at least four mice per group.
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fig4: Reduced survival of PD-1 KO P14 cells during T cell contraction. WT and PD-1 KO P14 cells were mixed at a 1:1 ratio (250 cells each), adoptively transferred into naive recipient mice, and infected with LCMV clone 13. P14 responses were then analyzed at the indicated time points. (A) Percent decrease in the frequency of WT and PD-1 KO P14 cells from peak of T cell response (day 15 p.i.) to chronic phase of infection (day 42 p.i.). Values indicate the mean percent decrease for each population. (B and C) Expression of LIVE/DEAD Aqua (B) and Annexin V (C) as a measure of cell death in WT and PD-1 KO P14 cells at day 18 p.i. in the spleen for individual (histograms) and multiple mice (bar graphs). Values indicate the frequency of P14 cells positive for staining based on FMO staining controls. (D) Expression of CD44 versus FLICA in WT and PD-1 KO P14 cells at day 14 p.i. in the spleen for individual (left) and multiple mice (right). Values indicate the frequency of P14 cells positive for FLICA dye based on FMO staining control. All error bars indicate ±SEM. *, P < 0.05; **, P < 0.01 (paired Student’s t test for B–D and unpaired Student’s t test for A) for all graphs (A–D). All data are representative of three independent experiments with at least four mice per group.
Mentions: We next examined how the absence of PD-1 affected the transition to later stages of infection. After peak expansion, PD-1 KO P14 cells underwent significantly greater contraction between days 15 and 42 p.i. (88% decrease) compared with WT P14 cells (75% decrease; Fig. 4 A). We hypothesized that this more dramatic contraction was caused by decreased survival in the absence of inhibitory signals from the PD-1 pathway. To test this possibility, WT and PD-1 KO P14 cells were assessed for markers of cell death between days 14 and 20 p.i. in the spleen. A higher frequency of PD-1 KO P14 cells stained with LIVE/DEAD Aqua (Fig. 4 B) and Annexin V (Fig. 4 C), markers of compromised cell membrane integrity which are associated with apoptosis and cell death. PD-1 KO P14 cells also displayed increased staining with fluorescent caspase substrates (FLICA) at day 15 p.i. (Fig. 4 D). In addition, ex vivo survival of PD-1 KO P14 cells was decreased, as demonstrated by a significant reduction in the total frequency of live cells remaining after a 10-h in vitro culture (not depicted). Thus, in the absence of PD-1, virus-specific CD8+ T cells experience considerably more cell death than WT CD8+ T cells of the same specificity in the same inflammatory environment. These findings suggest that PD-1 prevents overstimulation of CD8+ T cells and subsequent excessive cell death during chronic viral infection.

Bottom Line: Increased proliferation between days 8 and 14 postinfection is associated with subsequent decreased CD8(+) T cell survival and disruption of a critical proliferative hierarchy necessary to maintain exhausted populations long term.Ultimately, the absence of PD-1 leads to the accumulation of more cytotoxic, but terminally differentiated, CD8(+) TEX cells.They also highlight a novel role for PD-1 in preserving TEX cell populations from overstimulation, excessive proliferation, and terminal differentiation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology and Penn Institute for Immunology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104 Department of Microbiology and Penn Institute for Immunology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104.

Show MeSH
Related in: MedlinePlus