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B cells participate in thymic negative selection of murine auto-reactive CD4+ T cells.

Frommer F, Waisman A - PLoS ONE (2010)

Bottom Line: It is well documented that thymic epithelial cells participate in the process of negative selection in the thymus.Using a unique mouse model we show that B cells induce negative selection of self-reactive thymocytes in a process that leads to the deletion of these cells whereas regulatory T cells are spared.These findings have direct implication in autoimmunity, as expression of a myelin antigen by B cells in the thymus renders the mice resistant to autoimmune inflammation of the CNS.

View Article: PubMed Central - PubMed

Affiliation: Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, 55131 Mainz, Germany.

ABSTRACT
It is well documented that thymic epithelial cells participate in the process of negative selection in the thymus. In recent years it was reported that also dendritic cells enter the thymus and contribute to this process, thus allowing for the depletion of thymocytes that are specific to peripherally expressed self-antigens. Here we report that also B cells may take part in the elimination of auto-reactive thymocytes. Using a unique mouse model we show that B cells induce negative selection of self-reactive thymocytes in a process that leads to the deletion of these cells whereas regulatory T cells are spared. These findings have direct implication in autoimmunity, as expression of a myelin antigen by B cells in the thymus renders the mice resistant to autoimmune inflammation of the CNS.

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FACS analysis of Foxp3-expressing T cells in BMOG/2D2 mice.(A) Thymus and LN of WT 2D2 and BMOG/2D2 mice were analyzed for expression of Foxp3 by intracellular FACS staining. Genotypes and antibodies used are as indicated. Cells were gated on CD4+ cells. Numbers in quadrants indicate percent positive cells. (B) Total numbers of CD4+ Foxp3+ T cells from thymus and LN were calculated. Data represent mean values ± SEM of several individual experiments. ns, not significant. (C) LN cells from BMOG/2D2 and WT 2D2 mice were gated on CD4+ Va3.2+ or CD4+ Va3.2− T cells, respectively, and percentage of Foxp3-expressing cells among these populations is shown by histograms. The blue line in the histograms refers to the blue gate of CD4+ Va3.2− cells, the red line refers to CD4+ Va3.2+ cells (red gate). Colored numbers above the marker line indicate percent positive cells for the respective populations.
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pone-0015372-g004: FACS analysis of Foxp3-expressing T cells in BMOG/2D2 mice.(A) Thymus and LN of WT 2D2 and BMOG/2D2 mice were analyzed for expression of Foxp3 by intracellular FACS staining. Genotypes and antibodies used are as indicated. Cells were gated on CD4+ cells. Numbers in quadrants indicate percent positive cells. (B) Total numbers of CD4+ Foxp3+ T cells from thymus and LN were calculated. Data represent mean values ± SEM of several individual experiments. ns, not significant. (C) LN cells from BMOG/2D2 and WT 2D2 mice were gated on CD4+ Va3.2+ or CD4+ Va3.2− T cells, respectively, and percentage of Foxp3-expressing cells among these populations is shown by histograms. The blue line in the histograms refers to the blue gate of CD4+ Va3.2− cells, the red line refers to CD4+ Va3.2+ cells (red gate). Colored numbers above the marker line indicate percent positive cells for the respective populations.

Mentions: It was suggested that Foxp3 expression and thus development and function of regulatory T cells are dependent on the strength of TCR signaling during thymic selection [23]. To investigate whether the expression of self-peptide by B cells influences the number of regulatory T cells in the thymus, we analyzed the proportion of Foxp3+ T cells in BMOG/2D2 mice. As can be seen in Fig. 4A, the percentage of Foxp3+ T cells in the thymus of 2D2 mice is minimal, and accounts for only 0.5% of all CD4+ T cells. In contrast, we observed a 10-fold increase of Foxp3+ T cells in the thymus of BMOG/2D2 mice (Fig. 4A). Importantly, this increase is not due to increased total numbers of these cells (Fig. 4B), but reflects the decrease of the Foxp3− T cell population. As can be seen in Fig. 4C (and Fig. 1–3), very few CD4+Vα3.2+ T cells can be found in the LN of BMOG/2D2 mice when compared to LN of 2D2 WT mice. The decrease of MOG-specific T cells in the peripheral lymphoid organs of BMOG/2D2 mice is most likely due to the decrease in MOG-specific CD4+ T cells in the thymus of these mice, and as mentioned above, is suggested to occur upon deletion of antigen-specific T cells that encounter B cells presenting the MOG peptide in the thymus. Interestingly, when we analyzed the percentage of Foxp3+ T cells among the Vα3.2-expressing and non-expressing T cells, we found that in single transgenic 2D2 mice, a large proportion of Vα3.2 negative cells express this essential regulatory T cell transcription factor (Fig. 4C). In fact, this proportion, 27%, is much higher than normally seen in WT mice. It is a strong indication that the process of TCR editing in the thymus is coupled to the process of regulatory T cell generation. This proportion of Foxp3-expressing T cells among the Vα3.2 negative cells is slightly increased in BMOG/2D2 mice (Fig. 4C). But most importantly, the proportion of Foxp3-expressing T cells among the Vα3.2-expressing T cells is also greatly enhanced (Fig. 4C), leading to mice in which about a third of all CD4+ T cells are Foxp3+.


B cells participate in thymic negative selection of murine auto-reactive CD4+ T cells.

Frommer F, Waisman A - PLoS ONE (2010)

FACS analysis of Foxp3-expressing T cells in BMOG/2D2 mice.(A) Thymus and LN of WT 2D2 and BMOG/2D2 mice were analyzed for expression of Foxp3 by intracellular FACS staining. Genotypes and antibodies used are as indicated. Cells were gated on CD4+ cells. Numbers in quadrants indicate percent positive cells. (B) Total numbers of CD4+ Foxp3+ T cells from thymus and LN were calculated. Data represent mean values ± SEM of several individual experiments. ns, not significant. (C) LN cells from BMOG/2D2 and WT 2D2 mice were gated on CD4+ Va3.2+ or CD4+ Va3.2− T cells, respectively, and percentage of Foxp3-expressing cells among these populations is shown by histograms. The blue line in the histograms refers to the blue gate of CD4+ Va3.2− cells, the red line refers to CD4+ Va3.2+ cells (red gate). Colored numbers above the marker line indicate percent positive cells for the respective populations.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2958132&req=5

pone-0015372-g004: FACS analysis of Foxp3-expressing T cells in BMOG/2D2 mice.(A) Thymus and LN of WT 2D2 and BMOG/2D2 mice were analyzed for expression of Foxp3 by intracellular FACS staining. Genotypes and antibodies used are as indicated. Cells were gated on CD4+ cells. Numbers in quadrants indicate percent positive cells. (B) Total numbers of CD4+ Foxp3+ T cells from thymus and LN were calculated. Data represent mean values ± SEM of several individual experiments. ns, not significant. (C) LN cells from BMOG/2D2 and WT 2D2 mice were gated on CD4+ Va3.2+ or CD4+ Va3.2− T cells, respectively, and percentage of Foxp3-expressing cells among these populations is shown by histograms. The blue line in the histograms refers to the blue gate of CD4+ Va3.2− cells, the red line refers to CD4+ Va3.2+ cells (red gate). Colored numbers above the marker line indicate percent positive cells for the respective populations.
Mentions: It was suggested that Foxp3 expression and thus development and function of regulatory T cells are dependent on the strength of TCR signaling during thymic selection [23]. To investigate whether the expression of self-peptide by B cells influences the number of regulatory T cells in the thymus, we analyzed the proportion of Foxp3+ T cells in BMOG/2D2 mice. As can be seen in Fig. 4A, the percentage of Foxp3+ T cells in the thymus of 2D2 mice is minimal, and accounts for only 0.5% of all CD4+ T cells. In contrast, we observed a 10-fold increase of Foxp3+ T cells in the thymus of BMOG/2D2 mice (Fig. 4A). Importantly, this increase is not due to increased total numbers of these cells (Fig. 4B), but reflects the decrease of the Foxp3− T cell population. As can be seen in Fig. 4C (and Fig. 1–3), very few CD4+Vα3.2+ T cells can be found in the LN of BMOG/2D2 mice when compared to LN of 2D2 WT mice. The decrease of MOG-specific T cells in the peripheral lymphoid organs of BMOG/2D2 mice is most likely due to the decrease in MOG-specific CD4+ T cells in the thymus of these mice, and as mentioned above, is suggested to occur upon deletion of antigen-specific T cells that encounter B cells presenting the MOG peptide in the thymus. Interestingly, when we analyzed the percentage of Foxp3+ T cells among the Vα3.2-expressing and non-expressing T cells, we found that in single transgenic 2D2 mice, a large proportion of Vα3.2 negative cells express this essential regulatory T cell transcription factor (Fig. 4C). In fact, this proportion, 27%, is much higher than normally seen in WT mice. It is a strong indication that the process of TCR editing in the thymus is coupled to the process of regulatory T cell generation. This proportion of Foxp3-expressing T cells among the Vα3.2 negative cells is slightly increased in BMOG/2D2 mice (Fig. 4C). But most importantly, the proportion of Foxp3-expressing T cells among the Vα3.2-expressing T cells is also greatly enhanced (Fig. 4C), leading to mice in which about a third of all CD4+ T cells are Foxp3+.

Bottom Line: It is well documented that thymic epithelial cells participate in the process of negative selection in the thymus.Using a unique mouse model we show that B cells induce negative selection of self-reactive thymocytes in a process that leads to the deletion of these cells whereas regulatory T cells are spared.These findings have direct implication in autoimmunity, as expression of a myelin antigen by B cells in the thymus renders the mice resistant to autoimmune inflammation of the CNS.

View Article: PubMed Central - PubMed

Affiliation: Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, 55131 Mainz, Germany.

ABSTRACT
It is well documented that thymic epithelial cells participate in the process of negative selection in the thymus. In recent years it was reported that also dendritic cells enter the thymus and contribute to this process, thus allowing for the depletion of thymocytes that are specific to peripherally expressed self-antigens. Here we report that also B cells may take part in the elimination of auto-reactive thymocytes. Using a unique mouse model we show that B cells induce negative selection of self-reactive thymocytes in a process that leads to the deletion of these cells whereas regulatory T cells are spared. These findings have direct implication in autoimmunity, as expression of a myelin antigen by B cells in the thymus renders the mice resistant to autoimmune inflammation of the CNS.

Show MeSH
Related in: MedlinePlus