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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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Resting blood-derived human mucosal-associated invariant T ( MAIT) cells have a unique cytotoxic profile. (a) Expression of granzyme (Gr) B, perforin, GrA, and GrK in peripheral blood CD8+ T cells from healthy donors according to CD161 expression levels. For each marker, representative staining gated on CD8+ T cells (left), representative staining gated on CD161++, CD161+, and CD161− CD8+ T cells (middle), and cumulative data for 12–15 healthy individuals (right) are shown. Results shown as mean±s.e.m., 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. (b) CD161++CD8+ T cells are predominantly Vα7.2+, compared with CD161+ and CD161− CD8+ T cells. Representative staining of Vα7.2 T-cell receptor (TCR) on CD8+ T cells according to CD161 expression levels and cumulative data are shown (n=8). (c) Expression of GrB, perforin, GrA, and GrK in Vα7.2+ and Vα7.2− cells, gated within the CD161++CD8+ T-cell population. Cumulative data are shown, analyzed by paired t-test (n=8–12). (d) Representative images showing Imagestream analysis of colocalization of GrA, GrK, and CD107α expression within CD161++CD8+ T cells. Histograms of normalized cell frequency against colocalization as measured by Bright Detail Similarity scores; >2.0 is defined as colocalized (see Supplementary Methods).
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fig1: Resting blood-derived human mucosal-associated invariant T ( MAIT) cells have a unique cytotoxic profile. (a) Expression of granzyme (Gr) B, perforin, GrA, and GrK in peripheral blood CD8+ T cells from healthy donors according to CD161 expression levels. For each marker, representative staining gated on CD8+ T cells (left), representative staining gated on CD161++, CD161+, and CD161− CD8+ T cells (middle), and cumulative data for 12–15 healthy individuals (right) are shown. Results shown as mean±s.e.m., 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. (b) CD161++CD8+ T cells are predominantly Vα7.2+, compared with CD161+ and CD161− CD8+ T cells. Representative staining of Vα7.2 T-cell receptor (TCR) on CD8+ T cells according to CD161 expression levels and cumulative data are shown (n=8). (c) Expression of GrB, perforin, GrA, and GrK in Vα7.2+ and Vα7.2− cells, gated within the CD161++CD8+ T-cell population. Cumulative data are shown, analyzed by paired t-test (n=8–12). (d) Representative images showing Imagestream analysis of colocalization of GrA, GrK, and CD107α expression within CD161++CD8+ T cells. Histograms of normalized cell frequency against colocalization as measured by Bright Detail Similarity scores; >2.0 is defined as colocalized (see Supplementary Methods).

Mentions: First, we confirmed our previous finding12 that ex vivo, peripheral blood CD161++CD8+ T cells expressed almost no GrB (3.1±0.9%) compared with either CD161+ (47.6%, P<0.0001) or CD161− sub-populations (18.5%, P<0.01; Figure 1a). The amount of perforin expressed by these cells, as measured by geometric mean fluorescence intensity, was also significantly lower than other CD8+ T-cell sub-populations (both P<0.0001). In contrast, CD161++CD8+ T cells expressed high levels of GrA (96.6±1.2%) compared with CD161+ (87.2%, P<0.05) and CD161−CD8+ T cells (31.3%, P<0.0001). CD161++CD8+ T cells also uniquely expressed high levels of GrK (91.1±1.2%) compared with CD161+CD8+ T cells (32.9%, P<0.0001) and CD161−CD8+ T cells (16.3%, P<0.0001). Consistent with transcriptional profiling,11 cord blood CD161++CD8+ T cells were also GrA+GrK+ (Supplementary Figure S1A online), suggesting this is an inherent feature of this subset.


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)

Resting blood-derived human mucosal-associated invariant T ( MAIT) cells have a unique cytotoxic profile. (a) Expression of granzyme (Gr) B, perforin, GrA, and GrK in peripheral blood CD8+ T cells from healthy donors according to CD161 expression levels. For each marker, representative staining gated on CD8+ T cells (left), representative staining gated on CD161++, CD161+, and CD161− CD8+ T cells (middle), and cumulative data for 12–15 healthy individuals (right) are shown. Results shown as mean±s.e.m., 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. (b) CD161++CD8+ T cells are predominantly Vα7.2+, compared with CD161+ and CD161− CD8+ T cells. Representative staining of Vα7.2 T-cell receptor (TCR) on CD8+ T cells according to CD161 expression levels and cumulative data are shown (n=8). (c) Expression of GrB, perforin, GrA, and GrK in Vα7.2+ and Vα7.2− cells, gated within the CD161++CD8+ T-cell population. Cumulative data are shown, analyzed by paired t-test (n=8–12). (d) Representative images showing Imagestream analysis of colocalization of GrA, GrK, and CD107α expression within CD161++CD8+ T cells. Histograms of normalized cell frequency against colocalization as measured by Bright Detail Similarity scores; >2.0 is defined as colocalized (see Supplementary Methods).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig1: Resting blood-derived human mucosal-associated invariant T ( MAIT) cells have a unique cytotoxic profile. (a) Expression of granzyme (Gr) B, perforin, GrA, and GrK in peripheral blood CD8+ T cells from healthy donors according to CD161 expression levels. For each marker, representative staining gated on CD8+ T cells (left), representative staining gated on CD161++, CD161+, and CD161− CD8+ T cells (middle), and cumulative data for 12–15 healthy individuals (right) are shown. Results shown as mean±s.e.m., 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. (b) CD161++CD8+ T cells are predominantly Vα7.2+, compared with CD161+ and CD161− CD8+ T cells. Representative staining of Vα7.2 T-cell receptor (TCR) on CD8+ T cells according to CD161 expression levels and cumulative data are shown (n=8). (c) Expression of GrB, perforin, GrA, and GrK in Vα7.2+ and Vα7.2− cells, gated within the CD161++CD8+ T-cell population. Cumulative data are shown, analyzed by paired t-test (n=8–12). (d) Representative images showing Imagestream analysis of colocalization of GrA, GrK, and CD107α expression within CD161++CD8+ T cells. Histograms of normalized cell frequency against colocalization as measured by Bright Detail Similarity scores; >2.0 is defined as colocalized (see Supplementary Methods).
Mentions: First, we confirmed our previous finding12 that ex vivo, peripheral blood CD161++CD8+ T cells expressed almost no GrB (3.1±0.9%) compared with either CD161+ (47.6%, P<0.0001) or CD161− sub-populations (18.5%, P<0.01; Figure 1a). The amount of perforin expressed by these cells, as measured by geometric mean fluorescence intensity, was also significantly lower than other CD8+ T-cell sub-populations (both P<0.0001). In contrast, CD161++CD8+ T cells expressed high levels of GrA (96.6±1.2%) compared with CD161+ (87.2%, P<0.05) and CD161−CD8+ T cells (31.3%, P<0.0001). CD161++CD8+ T cells also uniquely expressed high levels of GrK (91.1±1.2%) compared with CD161+CD8+ T cells (32.9%, P<0.0001) and CD161−CD8+ T cells (16.3%, P<0.0001). Consistent with transcriptional profiling,11 cord blood CD161++CD8+ T cells were also GrA+GrK+ (Supplementary Figure S1A online), suggesting this is an inherent feature of this subset.

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