Limits...
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.

Show MeSH

Related in: MedlinePlus

IL-21–deficient mice form detectable GCs after immunization, but the kinetics of the GC is altered. (A and B) ELISA analysis of total serum IgG1 (A) and IgE (B) in unimmunized mice of the indicated genotypes. (C) Flow cytometric contour plots and graphical analysis of GL-7+Fas+ GC cells gated on live B220+ lymphocytes from Il21+/+ and Il21−/− mice at the indicated time points after SRBC immunization. Each symbol represents one mouse. (D) Photomicrographs of spleen sections stained for IgD (brown) and PNA (blue) from Il21+/+ and Il21−/− mice 8 d after immunization. Data are representative of two independent experiments (n ≥ 4 per group). Bars, 200 µm. (E) Flow cytometric histograms and graphical analysis of PNA binding on GL-7+Fas+B220+ GC B cells from Il21+/+ and Il21−/− mice 7 d after SRBC immunization. Statistically significant differences are indicated (*, P ≤ 0.05; **, P ≤ 0.01). Data are representative of two independent experiments, each symbol represents one mouse, and tops of bars are drawn through the median values. MFI, mean fluorescence intensity; ns, not significant.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC2822609&req=5

fig1: IL-21–deficient mice form detectable GCs after immunization, but the kinetics of the GC is altered. (A and B) ELISA analysis of total serum IgG1 (A) and IgE (B) in unimmunized mice of the indicated genotypes. (C) Flow cytometric contour plots and graphical analysis of GL-7+Fas+ GC cells gated on live B220+ lymphocytes from Il21+/+ and Il21−/− mice at the indicated time points after SRBC immunization. Each symbol represents one mouse. (D) Photomicrographs of spleen sections stained for IgD (brown) and PNA (blue) from Il21+/+ and Il21−/− mice 8 d after immunization. Data are representative of two independent experiments (n ≥ 4 per group). Bars, 200 µm. (E) Flow cytometric histograms and graphical analysis of PNA binding on GL-7+Fas+B220+ GC B cells from Il21+/+ and Il21−/− mice 7 d after SRBC immunization. Statistically significant differences are indicated (*, P ≤ 0.05; **, P ≤ 0.01). Data are representative of two independent experiments, each symbol represents one mouse, and tops of bars are drawn through the median values. MFI, mean fluorescence intensity; ns, not significant.

Mentions: To assess the role of IL-21 signaling in both GC and Tfh cell formation, we compared the responses of Il21+/+ and Il21−/− mice after TD immunization with sheep RBCs (SRBCs). Analysis of basal serum Igs revealed the reported reduction in serum IgG1 and elevated IgE titers in the absence of IL-21 (Fig. 1, A and B; Ozaki et al., 2002). The percentage of GC B cells identified by expression of GL-7 and Fas (CD95) was measured by flow cytometric analysis of splenocytes before or on days 6, 8, and 14 after immunization. Without immunization, IL-21–deficient mice have a reduction in the percentage of “background” GCs (P = 0.01). At day 6, there was a 40% reduction in the number of GC B cells in Il21−/− compared with Il21+/+ mice, reaching a 60% reduction by day 14 (P = 0.01; Fig. 1 C). These data demonstrate that IL-21 is not essential for initiating GC reactions but is required to reach GC peak numbers and maintain GC reactions.


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-21–deficient mice form detectable GCs after immunization, but the kinetics of the GC is altered. (A and B) ELISA analysis of total serum IgG1 (A) and IgE (B) in unimmunized mice of the indicated genotypes. (C) Flow cytometric contour plots and graphical analysis of GL-7+Fas+ GC cells gated on live B220+ lymphocytes from Il21+/+ and Il21−/− mice at the indicated time points after SRBC immunization. Each symbol represents one mouse. (D) Photomicrographs of spleen sections stained for IgD (brown) and PNA (blue) from Il21+/+ and Il21−/− mice 8 d after immunization. Data are representative of two independent experiments (n ≥ 4 per group). Bars, 200 µm. (E) Flow cytometric histograms and graphical analysis of PNA binding on GL-7+Fas+B220+ GC B cells from Il21+/+ and Il21−/− mice 7 d after SRBC immunization. Statistically significant differences are indicated (*, P ≤ 0.05; **, P ≤ 0.01). Data are representative of two independent experiments, each symbol represents one mouse, and tops of bars are drawn through the median values. MFI, mean fluorescence intensity; ns, not significant.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2822609&req=5

fig1: IL-21–deficient mice form detectable GCs after immunization, but the kinetics of the GC is altered. (A and B) ELISA analysis of total serum IgG1 (A) and IgE (B) in unimmunized mice of the indicated genotypes. (C) Flow cytometric contour plots and graphical analysis of GL-7+Fas+ GC cells gated on live B220+ lymphocytes from Il21+/+ and Il21−/− mice at the indicated time points after SRBC immunization. Each symbol represents one mouse. (D) Photomicrographs of spleen sections stained for IgD (brown) and PNA (blue) from Il21+/+ and Il21−/− mice 8 d after immunization. Data are representative of two independent experiments (n ≥ 4 per group). Bars, 200 µm. (E) Flow cytometric histograms and graphical analysis of PNA binding on GL-7+Fas+B220+ GC B cells from Il21+/+ and Il21−/− mice 7 d after SRBC immunization. Statistically significant differences are indicated (*, P ≤ 0.05; **, P ≤ 0.01). Data are representative of two independent experiments, each symbol represents one mouse, and tops of bars are drawn through the median values. MFI, mean fluorescence intensity; ns, not significant.
Mentions: To assess the role of IL-21 signaling in both GC and Tfh cell formation, we compared the responses of Il21+/+ and Il21−/− mice after TD immunization with sheep RBCs (SRBCs). Analysis of basal serum Igs revealed the reported reduction in serum IgG1 and elevated IgE titers in the absence of IL-21 (Fig. 1, A and B; Ozaki et al., 2002). The percentage of GC B cells identified by expression of GL-7 and Fas (CD95) was measured by flow cytometric analysis of splenocytes before or on days 6, 8, and 14 after immunization. Without immunization, IL-21–deficient mice have a reduction in the percentage of “background” GCs (P = 0.01). At day 6, there was a 40% reduction in the number of GC B cells in Il21−/− compared with Il21+/+ mice, reaching a 60% reduction by day 14 (P = 0.01; Fig. 1 C). These data demonstrate that IL-21 is not essential for initiating GC reactions but is required to reach GC peak numbers and maintain GC reactions.

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