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Cutting edge: circulating plasmablasts induce the differentiation of human T follicular helper cells via IL-6 production.

Chavele KM, Merry E, Ehrenstein MR - J. Immunol. (2015)

Bottom Line: In this article, we reveal a reciprocal interaction whereby circulating human plasmablasts are potent inducers of the Tfh cell-differentiation program, including the expression of their key transcription factor Bcl-6.The markedly increased propensity of plasmablasts, compared with naive B cells, to induce Tfh cell differentiation was due to their increased production of IL-6.Our data uncover a positive-feedback loop between circulating plasmablasts and Tfh cells that could sustain autoimmunity and spread Ab-driven inflammation to unaffected sites; this represents an important therapeutic target, as well as reveals a novel mechanism of action for tocilizumab.

View Article: PubMed Central - PubMed

Affiliation: Centre for Rheumatology, Division of Medicine, University College London, London WC1E 6JF, United Kingdom.

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Plasmablasts induce the differentiation of Tfh cells. Naive T cells together with naive B cells, memory B cells, plasmablasts, or monocytes were stimulated with anti-CD3/CD28 for 4 d. (A) Representative flow cytometry plots (gated on CD4+ T cells) and cumulative data showing the percentage of Tfh cells (n = 35, mean ± SE). (B) Representative graphs showing Bcl-6 expression in Tfh cells induced in the presence of plasmablasts; mean fluorescence intensity value is indicated. (C) Representative flow cytometry plots and cumulative data showing the percentage of Tfh cells expressing IL-21 in cultures of naive T cells with naive B cells or plasmablasts (n = 9, mean ± SE). CD4+ T cells were repurified from cultures of naive T cells alone (TfhNT) or with plasmablasts (TfhPL) (day 4) and cocultured with freshly isolated autologous naive (D) or memory (E) B cells in the presence of Staphylococcal enterotoxin B for 10 d. IgM and IgG Ab production was measured by ELISA (n = 5, mean ± SE). **p < 0.001, ***p < 0.0001.
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fig02: Plasmablasts induce the differentiation of Tfh cells. Naive T cells together with naive B cells, memory B cells, plasmablasts, or monocytes were stimulated with anti-CD3/CD28 for 4 d. (A) Representative flow cytometry plots (gated on CD4+ T cells) and cumulative data showing the percentage of Tfh cells (n = 35, mean ± SE). (B) Representative graphs showing Bcl-6 expression in Tfh cells induced in the presence of plasmablasts; mean fluorescence intensity value is indicated. (C) Representative flow cytometry plots and cumulative data showing the percentage of Tfh cells expressing IL-21 in cultures of naive T cells with naive B cells or plasmablasts (n = 9, mean ± SE). CD4+ T cells were repurified from cultures of naive T cells alone (TfhNT) or with plasmablasts (TfhPL) (day 4) and cocultured with freshly isolated autologous naive (D) or memory (E) B cells in the presence of Staphylococcal enterotoxin B for 10 d. IgM and IgG Ab production was measured by ELISA (n = 5, mean ± SE). **p < 0.001, ***p < 0.0001.

Mentions: We next assessed whether circulating plasmablasts possessed the capacity to induce the differentiation of Tfh cells from naive T cells. Thus, plasmablasts, naive and memory B cells, and monocytes were isolated and added to naive T cells in the presence of anti-CD3/CD28. Plasmablasts were the most potent inducers of Tfh cell differentiation (Fig. 2A). Tfh cells induced in the presence of plasmablasts expressed high levels of PD-1 (Supplemental Fig. 1E) and Bcl-6 (Fig. 2B). In addition, plasmablast-induced Tfh cells secreted significantly more IL-21 compared with naive B cell–induced Tfh cells (Fig. 2C). Although naive B cells possessed some ability to induce Tfh cell differentiation, this could be explained, in part, by the formation of plasmablasts from naive B cells during the culture (Supplemental Fig. 1F). Indeed, the percentage of Tfh cells correlated with the numbers of plasmablasts present in these “naive B cell” cultures (Supplemental Fig. 1G). This finding suggests that the induction of Tfh cell differentiation was due, in part, to newly formed plasmablasts from naive B cells, although other mechanisms may contribute, given that monocytes can increase the number of Tfh cells above that seen with naive T cells alone. To support this finding we cocultured different ratios of naive CD4+ T cells/plasmablasts and assessed the induction of Tfh cell differentiation. The ratio of plasmablasts/naive CD4+ T cells in these cultures was directly proportional to Tfh cell differentiation (Supplemental Fig. 1H). To ascertain whether the differentiated Tfh cells were functional, T cells were repurified after 4 d of culture with plasmablasts and incubated with freshly isolated autologous naive B cells or memory B cells, as previously described (6). Plasmablast-induced Tfh cells provided enhanced B cell help and supported naive B cells and memory B cells to produce significantly more IgM (Fig. 2D) and IgG (Fig. 2E), respectively, compared with T cells that had not been exposed to plasmablasts. To our knowledge, our results show for the first time that human plasmablasts are potent inducers of Tfh cell differentiation. Of relevance, murine plasma cells were shown to inhibit, rather than promote, Tfh cell formation (7). This discrepancy may reflect differences between plasma cells and circulating plasmablasts, or it could be due to differential regulation of Tfh cells in mice and humans.


Cutting edge: circulating plasmablasts induce the differentiation of human T follicular helper cells via IL-6 production.

Chavele KM, Merry E, Ehrenstein MR - J. Immunol. (2015)

Plasmablasts induce the differentiation of Tfh cells. Naive T cells together with naive B cells, memory B cells, plasmablasts, or monocytes were stimulated with anti-CD3/CD28 for 4 d. (A) Representative flow cytometry plots (gated on CD4+ T cells) and cumulative data showing the percentage of Tfh cells (n = 35, mean ± SE). (B) Representative graphs showing Bcl-6 expression in Tfh cells induced in the presence of plasmablasts; mean fluorescence intensity value is indicated. (C) Representative flow cytometry plots and cumulative data showing the percentage of Tfh cells expressing IL-21 in cultures of naive T cells with naive B cells or plasmablasts (n = 9, mean ± SE). CD4+ T cells were repurified from cultures of naive T cells alone (TfhNT) or with plasmablasts (TfhPL) (day 4) and cocultured with freshly isolated autologous naive (D) or memory (E) B cells in the presence of Staphylococcal enterotoxin B for 10 d. IgM and IgG Ab production was measured by ELISA (n = 5, mean ± SE). **p < 0.001, ***p < 0.0001.
© Copyright Policy - creative-commons
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fig02: Plasmablasts induce the differentiation of Tfh cells. Naive T cells together with naive B cells, memory B cells, plasmablasts, or monocytes were stimulated with anti-CD3/CD28 for 4 d. (A) Representative flow cytometry plots (gated on CD4+ T cells) and cumulative data showing the percentage of Tfh cells (n = 35, mean ± SE). (B) Representative graphs showing Bcl-6 expression in Tfh cells induced in the presence of plasmablasts; mean fluorescence intensity value is indicated. (C) Representative flow cytometry plots and cumulative data showing the percentage of Tfh cells expressing IL-21 in cultures of naive T cells with naive B cells or plasmablasts (n = 9, mean ± SE). CD4+ T cells were repurified from cultures of naive T cells alone (TfhNT) or with plasmablasts (TfhPL) (day 4) and cocultured with freshly isolated autologous naive (D) or memory (E) B cells in the presence of Staphylococcal enterotoxin B for 10 d. IgM and IgG Ab production was measured by ELISA (n = 5, mean ± SE). **p < 0.001, ***p < 0.0001.
Mentions: We next assessed whether circulating plasmablasts possessed the capacity to induce the differentiation of Tfh cells from naive T cells. Thus, plasmablasts, naive and memory B cells, and monocytes were isolated and added to naive T cells in the presence of anti-CD3/CD28. Plasmablasts were the most potent inducers of Tfh cell differentiation (Fig. 2A). Tfh cells induced in the presence of plasmablasts expressed high levels of PD-1 (Supplemental Fig. 1E) and Bcl-6 (Fig. 2B). In addition, plasmablast-induced Tfh cells secreted significantly more IL-21 compared with naive B cell–induced Tfh cells (Fig. 2C). Although naive B cells possessed some ability to induce Tfh cell differentiation, this could be explained, in part, by the formation of plasmablasts from naive B cells during the culture (Supplemental Fig. 1F). Indeed, the percentage of Tfh cells correlated with the numbers of plasmablasts present in these “naive B cell” cultures (Supplemental Fig. 1G). This finding suggests that the induction of Tfh cell differentiation was due, in part, to newly formed plasmablasts from naive B cells, although other mechanisms may contribute, given that monocytes can increase the number of Tfh cells above that seen with naive T cells alone. To support this finding we cocultured different ratios of naive CD4+ T cells/plasmablasts and assessed the induction of Tfh cell differentiation. The ratio of plasmablasts/naive CD4+ T cells in these cultures was directly proportional to Tfh cell differentiation (Supplemental Fig. 1H). To ascertain whether the differentiated Tfh cells were functional, T cells were repurified after 4 d of culture with plasmablasts and incubated with freshly isolated autologous naive B cells or memory B cells, as previously described (6). Plasmablast-induced Tfh cells provided enhanced B cell help and supported naive B cells and memory B cells to produce significantly more IgM (Fig. 2D) and IgG (Fig. 2E), respectively, compared with T cells that had not been exposed to plasmablasts. To our knowledge, our results show for the first time that human plasmablasts are potent inducers of Tfh cell differentiation. Of relevance, murine plasma cells were shown to inhibit, rather than promote, Tfh cell formation (7). This discrepancy may reflect differences between plasma cells and circulating plasmablasts, or it could be due to differential regulation of Tfh cells in mice and humans.

Bottom Line: In this article, we reveal a reciprocal interaction whereby circulating human plasmablasts are potent inducers of the Tfh cell-differentiation program, including the expression of their key transcription factor Bcl-6.The markedly increased propensity of plasmablasts, compared with naive B cells, to induce Tfh cell differentiation was due to their increased production of IL-6.Our data uncover a positive-feedback loop between circulating plasmablasts and Tfh cells that could sustain autoimmunity and spread Ab-driven inflammation to unaffected sites; this represents an important therapeutic target, as well as reveals a novel mechanism of action for tocilizumab.

View Article: PubMed Central - PubMed

Affiliation: Centre for Rheumatology, Division of Medicine, University College London, London WC1E 6JF, United Kingdom.

Show MeSH
Related in: MedlinePlus