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MAIT cells are licensed through granzyme exchange to kill bacterially sensitized targets.

Kurioka A, Ussher JE, Cosgrove C, Clough C, Fergusson JR, Smith K, Kang YH, Walker LJ, Hansen TH, Willberg CB, Klenerman P - Mucosal Immunol (2014)

Bottom Line: Mucosal-associated invariant T (MAIT) cells are an innate-like T-cell population restricted by the non-polymorphic, major histocompatibility complex class I-related protein 1, MR1.We show that resting human MAIT cells are uniquely characterized by a lack of granzyme (Gr) B and low perforin expression, key granule proteins required for efficient cytotoxic activity, but high levels of expression of GrA and GrK.Finally, we show that MAIT cells are highly proliferative in response to antigenic and cytokine stimulation, maintaining high expression of GrB, perforin, and GrA, but reduced expression of GrK following antigenic proliferation.

View Article: PubMed Central - PubMed

Affiliation: Peter Medawar Building for Pathogen Research, Nuffield Department of Medicine, University of Oxford, Oxford, UK.

ABSTRACT
Mucosal-associated invariant T (MAIT) cells are an innate-like T-cell population restricted by the non-polymorphic, major histocompatibility complex class I-related protein 1, MR1. MAIT cells are activated by a broad range of bacteria through detection of riboflavin metabolites bound by MR1, but their direct cytolytic capacity upon recognition of cognate target cells remains unclear. We show that resting human MAIT cells are uniquely characterized by a lack of granzyme (Gr) B and low perforin expression, key granule proteins required for efficient cytotoxic activity, but high levels of expression of GrA and GrK. Bacterial activation of MAIT cells rapidly induced GrB and perforin, licensing these cells to kill their cognate target cells. Using a novel flow cytometry-based killing assay, we show that licensed MAIT cells, but not ex vivo MAIT cells from the same donors, can efficiently kill Escherichia coli-exposed B-cell lines in an MR1- and degranulation-dependent manner. Finally, we show that MAIT cells are highly proliferative in response to antigenic and cytokine stimulation, maintaining high expression of GrB, perforin, and GrA, but reduced expression of GrK following antigenic proliferation. The tightly regulated cytolytic capacity of MAIT cells may have an important role in the control of intracellular bacterial infections, such as Mycobacterium tuberculosis.

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Bacterial stimulation leads to degranulation and changes in cytotoxic profile of mucosal-associated invariant T (MAIT) cells. Enriched CD8+ T cells were cocultured with THP1 cells exposed to E. coli, in the presence or absence of blocking antibodies against MR1, interleukin (IL)-12, IL-18 or isotype controls, and assayed for the expression of (a) CD107α, (b) granzyme (Gr) B, (c) perforin, (d) GrK, and (e) GrA. Representative plots gated on CD8+ T cells are shown on the left panel and cumulative data on the right panel for each marker, with bars indicating mean±s.e.m. (n=7–10). Staining control shows isotype control (conjugated with matched fluorochromes) used for gating for each marker. Note that GrA and GrK staining control is the same for each donor as both conjugated to the same flurochrome, and CD107α staining uses the unstimulated control for gating. Results are analyzed by repeated-measures one-way analysis of variance (ANOVA), with Bonferroni's multiple comparisons test. *P<0.05, **P<0.01, ***P<0.001, ****P<0.0001.
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fig2: Bacterial stimulation leads to degranulation and changes in cytotoxic profile of mucosal-associated invariant T (MAIT) cells. Enriched CD8+ T cells were cocultured with THP1 cells exposed to E. coli, in the presence or absence of blocking antibodies against MR1, interleukin (IL)-12, IL-18 or isotype controls, and assayed for the expression of (a) CD107α, (b) granzyme (Gr) B, (c) perforin, (d) GrK, and (e) GrA. Representative plots gated on CD8+ T cells are shown on the left panel and cumulative data on the right panel for each marker, with bars indicating mean±s.e.m. (n=7–10). Staining control shows isotype control (conjugated with matched fluorochromes) used for gating for each marker. Note that GrA and GrK staining control is the same for each donor as both conjugated to the same flurochrome, and CD107α staining uses the unstimulated control for gating. Results are analyzed by repeated-measures one-way analysis of variance (ANOVA), with Bonferroni's multiple comparisons test. *P<0.05, **P<0.01, ***P<0.001, ****P<0.0001.

Mentions: Using our previously described model,13 THP1 cell lines were pre-exposed to paraformaldehyde (PFA)-fixed Escherichia coli, and then cultured with enriched CD8+ T cells overnight, after which the cytotoxic profile of MAIT cells was evaluated (Figure 2). MAIT cells degranulated extensively in response to E. coli as measured by CD107α expression (Figure 2a; 66.3%, P<0.0001). This was almost completely blocked by an anti-MR1-blocking antibody (20.9% P<0.0001), whereas blocking IL-12 or IL-18 had minimal effect on the degranulation of the cells.


MAIT cells are licensed through granzyme exchange to kill bacterially sensitized targets.

Kurioka A, Ussher JE, Cosgrove C, Clough C, Fergusson JR, Smith K, Kang YH, Walker LJ, Hansen TH, Willberg CB, Klenerman P - Mucosal Immunol (2014)

Bacterial stimulation leads to degranulation and changes in cytotoxic profile of mucosal-associated invariant T (MAIT) cells. Enriched CD8+ T cells were cocultured with THP1 cells exposed to E. coli, in the presence or absence of blocking antibodies against MR1, interleukin (IL)-12, IL-18 or isotype controls, and assayed for the expression of (a) CD107α, (b) granzyme (Gr) B, (c) perforin, (d) GrK, and (e) GrA. Representative plots gated on CD8+ T cells are shown on the left panel and cumulative data on the right panel for each marker, with bars indicating mean±s.e.m. (n=7–10). Staining control shows isotype control (conjugated with matched fluorochromes) used for gating for each marker. Note that GrA and GrK staining control is the same for each donor as both conjugated to the same flurochrome, and CD107α staining uses the unstimulated control for gating. Results are analyzed by repeated-measures one-way analysis of variance (ANOVA), with Bonferroni's multiple comparisons test. *P<0.05, **P<0.01, ***P<0.001, ****P<0.0001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4288950&req=5

fig2: Bacterial stimulation leads to degranulation and changes in cytotoxic profile of mucosal-associated invariant T (MAIT) cells. Enriched CD8+ T cells were cocultured with THP1 cells exposed to E. coli, in the presence or absence of blocking antibodies against MR1, interleukin (IL)-12, IL-18 or isotype controls, and assayed for the expression of (a) CD107α, (b) granzyme (Gr) B, (c) perforin, (d) GrK, and (e) GrA. Representative plots gated on CD8+ T cells are shown on the left panel and cumulative data on the right panel for each marker, with bars indicating mean±s.e.m. (n=7–10). Staining control shows isotype control (conjugated with matched fluorochromes) used for gating for each marker. Note that GrA and GrK staining control is the same for each donor as both conjugated to the same flurochrome, and CD107α staining uses the unstimulated control for gating. Results are analyzed by repeated-measures one-way analysis of variance (ANOVA), with Bonferroni's multiple comparisons test. *P<0.05, **P<0.01, ***P<0.001, ****P<0.0001.
Mentions: Using our previously described model,13 THP1 cell lines were pre-exposed to paraformaldehyde (PFA)-fixed Escherichia coli, and then cultured with enriched CD8+ T cells overnight, after which the cytotoxic profile of MAIT cells was evaluated (Figure 2). MAIT cells degranulated extensively in response to E. coli as measured by CD107α expression (Figure 2a; 66.3%, P<0.0001). This was almost completely blocked by an anti-MR1-blocking antibody (20.9% P<0.0001), whereas blocking IL-12 or IL-18 had minimal effect on the degranulation of the cells.

Bottom Line: Mucosal-associated invariant T (MAIT) cells are an innate-like T-cell population restricted by the non-polymorphic, major histocompatibility complex class I-related protein 1, MR1.We show that resting human MAIT cells are uniquely characterized by a lack of granzyme (Gr) B and low perforin expression, key granule proteins required for efficient cytotoxic activity, but high levels of expression of GrA and GrK.Finally, we show that MAIT cells are highly proliferative in response to antigenic and cytokine stimulation, maintaining high expression of GrB, perforin, and GrA, but reduced expression of GrK following antigenic proliferation.

View Article: PubMed Central - PubMed

Affiliation: Peter Medawar Building for Pathogen Research, Nuffield Department of Medicine, University of Oxford, Oxford, UK.

ABSTRACT
Mucosal-associated invariant T (MAIT) cells are an innate-like T-cell population restricted by the non-polymorphic, major histocompatibility complex class I-related protein 1, MR1. MAIT cells are activated by a broad range of bacteria through detection of riboflavin metabolites bound by MR1, but their direct cytolytic capacity upon recognition of cognate target cells remains unclear. We show that resting human MAIT cells are uniquely characterized by a lack of granzyme (Gr) B and low perforin expression, key granule proteins required for efficient cytotoxic activity, but high levels of expression of GrA and GrK. Bacterial activation of MAIT cells rapidly induced GrB and perforin, licensing these cells to kill their cognate target cells. Using a novel flow cytometry-based killing assay, we show that licensed MAIT cells, but not ex vivo MAIT cells from the same donors, can efficiently kill Escherichia coli-exposed B-cell lines in an MR1- and degranulation-dependent manner. Finally, we show that MAIT cells are highly proliferative in response to antigenic and cytokine stimulation, maintaining high expression of GrB, perforin, and GrA, but reduced expression of GrK following antigenic proliferation. The tightly regulated cytolytic capacity of MAIT cells may have an important role in the control of intracellular bacterial infections, such as Mycobacterium tuberculosis.

Show MeSH
Related in: MedlinePlus