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IL-21 acts directly on B cells to regulate Bcl-6 expression and germinal center responses.

Linterman MA, Beaton L, Yu D, Ramiscal RR, Srivastava M, Hogan JJ, Verma NK, Smyth MJ, Rigby RJ, Vinuesa CG - J. Exp. Med. (2010)

Bottom Line: To date, it is unclear whether the effect of IL-21 on GC formation is predominantly a consequence of this cytokine acting directly on the Tfh cells or if IL-21 directly influences GC B cells.IL-21 deficiency profoundly impaired affinity maturation and reduced the proportion of IgG1(+) GC B cells but did not affect formation of early memory B cells.In contrast to the requirement for IL-21 in the follicular response to sheep red blood cells, a purely extrafollicular antibody response to Salmonella dominated by IgG2a was intact in the absence of IL-21.

View Article: PubMed Central - HTML - PubMed

Affiliation: John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia.

ABSTRACT
During T cell-dependent responses, B cells can either differentiate extrafollicularly into short-lived plasma cells or enter follicles to form germinal centers (GCs). Interactions with T follicular helper (Tfh) cells are required for GC formation and for selection of somatically mutated GC B cells. Interleukin (IL)-21 has been reported to play a role in Tfh cell formation and in B cell growth, survival, and isotype switching. To date, it is unclear whether the effect of IL-21 on GC formation is predominantly a consequence of this cytokine acting directly on the Tfh cells or if IL-21 directly influences GC B cells. We show that IL-21 acts in a B cell-intrinsic fashion to control GC B cell formation. Mixed bone marrow chimeras identified a significant B cell-autonomous effect of IL-21 receptor (R) signaling throughout all stages of the GC response. IL-21 deficiency profoundly impaired affinity maturation and reduced the proportion of IgG1(+) GC B cells but did not affect formation of early memory B cells. IL-21R was required on GC B cells for maximal expression of Bcl-6. In contrast to the requirement for IL-21 in the follicular response to sheep red blood cells, a purely extrafollicular antibody response to Salmonella dominated by IgG2a was intact in the absence of IL-21.

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IL-21R expression is required on both GC B cells and Tfh cells for their maintenance but is dispensable for their formation. (A and B) Gating strategy (A) and bar graphs (B) of mixed bone marrow chimeras containing a 1:1 ratio of control Il21r+/+CD45.1/Il21r+/+CD45.2 or Il21r+/+CD45.1/Il21r−/−CD45.2 bone marrow. Spleens from unimmunized mice (A; and B, top) or from mice immunized with SRBCs 6 or 14 d previously (B, middle and bottom) were analyzed by flow cytometry for the percentage of B220+ B cells that are CD45.2+ (B220+), the percentage of GL-7+Fas+ GC cells among B220+ cells that are CD45.2+ (GC cells), the percentage of CD4+ Th cells that are CD45.2+ (CD4+), and the percentage of CXCR5highPD-1high Tfh cells among CD4+ cells that are CD45.2+ (Tfh cells). Each bar represents a single recipient mouse; individual mice have been numbered and placed in the same order in each of the plots. Statistically significant decreases are indicated (*, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001). Data are representative of two independent experiments. (C and D) Gating strategy (C) and dot plots (D) of the proportion of B220+, GC (B220+Fas+GL-7+), and IgG1+ GC (B220+Fas+GL-7+IgG1+) cells derived from the CD45.2 compartment of mixed chimeras reconstituted with a 1:1 ratio of either CD45.1 Il21r+/+/CD45.2 Il21r+/+ (left) or CD45.1 Il21r+/+/CD45.2 Il21r−/− (right) bone marrow before (C; and D, top) or 6 d after SRBC immunization (D, bottom). In D, each number represents a single recipient mouse from two separate groups of the chimeric mice indicated above the left and right panels.
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fig3: IL-21R expression is required on both GC B cells and Tfh cells for their maintenance but is dispensable for their formation. (A and B) Gating strategy (A) and bar graphs (B) of mixed bone marrow chimeras containing a 1:1 ratio of control Il21r+/+CD45.1/Il21r+/+CD45.2 or Il21r+/+CD45.1/Il21r−/−CD45.2 bone marrow. Spleens from unimmunized mice (A; and B, top) or from mice immunized with SRBCs 6 or 14 d previously (B, middle and bottom) were analyzed by flow cytometry for the percentage of B220+ B cells that are CD45.2+ (B220+), the percentage of GL-7+Fas+ GC cells among B220+ cells that are CD45.2+ (GC cells), the percentage of CD4+ Th cells that are CD45.2+ (CD4+), and the percentage of CXCR5highPD-1high Tfh cells among CD4+ cells that are CD45.2+ (Tfh cells). Each bar represents a single recipient mouse; individual mice have been numbered and placed in the same order in each of the plots. Statistically significant decreases are indicated (*, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001). Data are representative of two independent experiments. (C and D) Gating strategy (C) and dot plots (D) of the proportion of B220+, GC (B220+Fas+GL-7+), and IgG1+ GC (B220+Fas+GL-7+IgG1+) cells derived from the CD45.2 compartment of mixed chimeras reconstituted with a 1:1 ratio of either CD45.1 Il21r+/+/CD45.2 Il21r+/+ (left) or CD45.1 Il21r+/+/CD45.2 Il21r−/− (right) bone marrow before (C; and D, top) or 6 d after SRBC immunization (D, bottom). In D, each number represents a single recipient mouse from two separate groups of the chimeric mice indicated above the left and right panels.

Mentions: To investigate whether IL-21R signaling in the B cells themselves is required for GC formation, we generated Il21r+/+/Il21r−/− mixed bone marrow chimeras. Sublethally irradiated Rag1−/− mice were reconstituted with a 1:1 mix of either CD45.1 Il21r+/+/CD45.2 Il21r+/+ or CD45.1 Il21r+/+/CD45.2 Il21r−/− bone marrow. 8 wk later, chimeric mice were immunized with SRBCs and the percentage of B220+ cells, GL-7+Fas+B220+ GC B cells, CD4+ T cells, and CXCR5highPD-1high CD4+ Tfh cells derived from the CD45.2 (Il21r−/− or control Il21r+/+) donor marrow in each mouse was determined (Fig. 3, A and B; and Fig. S3).


IL-21 acts directly on B cells to regulate Bcl-6 expression and germinal center responses.

Linterman MA, Beaton L, Yu D, Ramiscal RR, Srivastava M, Hogan JJ, Verma NK, Smyth MJ, Rigby RJ, Vinuesa CG - J. Exp. Med. (2010)

IL-21R expression is required on both GC B cells and Tfh cells for their maintenance but is dispensable for their formation. (A and B) Gating strategy (A) and bar graphs (B) of mixed bone marrow chimeras containing a 1:1 ratio of control Il21r+/+CD45.1/Il21r+/+CD45.2 or Il21r+/+CD45.1/Il21r−/−CD45.2 bone marrow. Spleens from unimmunized mice (A; and B, top) or from mice immunized with SRBCs 6 or 14 d previously (B, middle and bottom) were analyzed by flow cytometry for the percentage of B220+ B cells that are CD45.2+ (B220+), the percentage of GL-7+Fas+ GC cells among B220+ cells that are CD45.2+ (GC cells), the percentage of CD4+ Th cells that are CD45.2+ (CD4+), and the percentage of CXCR5highPD-1high Tfh cells among CD4+ cells that are CD45.2+ (Tfh cells). Each bar represents a single recipient mouse; individual mice have been numbered and placed in the same order in each of the plots. Statistically significant decreases are indicated (*, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001). Data are representative of two independent experiments. (C and D) Gating strategy (C) and dot plots (D) of the proportion of B220+, GC (B220+Fas+GL-7+), and IgG1+ GC (B220+Fas+GL-7+IgG1+) cells derived from the CD45.2 compartment of mixed chimeras reconstituted with a 1:1 ratio of either CD45.1 Il21r+/+/CD45.2 Il21r+/+ (left) or CD45.1 Il21r+/+/CD45.2 Il21r−/− (right) bone marrow before (C; and D, top) or 6 d after SRBC immunization (D, bottom). In D, each number represents a single recipient mouse from two separate groups of the chimeric mice indicated above the left and right panels.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC2822609&req=5

fig3: IL-21R expression is required on both GC B cells and Tfh cells for their maintenance but is dispensable for their formation. (A and B) Gating strategy (A) and bar graphs (B) of mixed bone marrow chimeras containing a 1:1 ratio of control Il21r+/+CD45.1/Il21r+/+CD45.2 or Il21r+/+CD45.1/Il21r−/−CD45.2 bone marrow. Spleens from unimmunized mice (A; and B, top) or from mice immunized with SRBCs 6 or 14 d previously (B, middle and bottom) were analyzed by flow cytometry for the percentage of B220+ B cells that are CD45.2+ (B220+), the percentage of GL-7+Fas+ GC cells among B220+ cells that are CD45.2+ (GC cells), the percentage of CD4+ Th cells that are CD45.2+ (CD4+), and the percentage of CXCR5highPD-1high Tfh cells among CD4+ cells that are CD45.2+ (Tfh cells). Each bar represents a single recipient mouse; individual mice have been numbered and placed in the same order in each of the plots. Statistically significant decreases are indicated (*, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001). Data are representative of two independent experiments. (C and D) Gating strategy (C) and dot plots (D) of the proportion of B220+, GC (B220+Fas+GL-7+), and IgG1+ GC (B220+Fas+GL-7+IgG1+) cells derived from the CD45.2 compartment of mixed chimeras reconstituted with a 1:1 ratio of either CD45.1 Il21r+/+/CD45.2 Il21r+/+ (left) or CD45.1 Il21r+/+/CD45.2 Il21r−/− (right) bone marrow before (C; and D, top) or 6 d after SRBC immunization (D, bottom). In D, each number represents a single recipient mouse from two separate groups of the chimeric mice indicated above the left and right panels.
Mentions: To investigate whether IL-21R signaling in the B cells themselves is required for GC formation, we generated Il21r+/+/Il21r−/− mixed bone marrow chimeras. Sublethally irradiated Rag1−/− mice were reconstituted with a 1:1 mix of either CD45.1 Il21r+/+/CD45.2 Il21r+/+ or CD45.1 Il21r+/+/CD45.2 Il21r−/− bone marrow. 8 wk later, chimeric mice were immunized with SRBCs and the percentage of B220+ cells, GL-7+Fas+B220+ GC B cells, CD4+ T cells, and CXCR5highPD-1high CD4+ Tfh cells derived from the CD45.2 (Il21r−/− or control Il21r+/+) donor marrow in each mouse was determined (Fig. 3, A and B; and Fig. S3).

Bottom Line: To date, it is unclear whether the effect of IL-21 on GC formation is predominantly a consequence of this cytokine acting directly on the Tfh cells or if IL-21 directly influences GC B cells.IL-21 deficiency profoundly impaired affinity maturation and reduced the proportion of IgG1(+) GC B cells but did not affect formation of early memory B cells.In contrast to the requirement for IL-21 in the follicular response to sheep red blood cells, a purely extrafollicular antibody response to Salmonella dominated by IgG2a was intact in the absence of IL-21.

View Article: PubMed Central - HTML - PubMed

Affiliation: John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia.

ABSTRACT
During T cell-dependent responses, B cells can either differentiate extrafollicularly into short-lived plasma cells or enter follicles to form germinal centers (GCs). Interactions with T follicular helper (Tfh) cells are required for GC formation and for selection of somatically mutated GC B cells. Interleukin (IL)-21 has been reported to play a role in Tfh cell formation and in B cell growth, survival, and isotype switching. To date, it is unclear whether the effect of IL-21 on GC formation is predominantly a consequence of this cytokine acting directly on the Tfh cells or if IL-21 directly influences GC B cells. We show that IL-21 acts in a B cell-intrinsic fashion to control GC B cell formation. Mixed bone marrow chimeras identified a significant B cell-autonomous effect of IL-21 receptor (R) signaling throughout all stages of the GC response. IL-21 deficiency profoundly impaired affinity maturation and reduced the proportion of IgG1(+) GC B cells but did not affect formation of early memory B cells. IL-21R was required on GC B cells for maximal expression of Bcl-6. In contrast to the requirement for IL-21 in the follicular response to sheep red blood cells, a purely extrafollicular antibody response to Salmonella dominated by IgG2a was intact in the absence of IL-21.

Show MeSH
Related in: MedlinePlus