Follicular regulatory T cells inhibit the development of granzyme B–expressing follicular helper T cells
Markus M. Xie, … , Jun Wan, Alexander L. Dent
Markus M. Xie, … , Jun Wan, Alexander L. Dent
Published August 22, 2019
Citation Information: JCI Insight. 2019;4(16):e128076. https://doi.org/10.1172/jci.insight.128076.
View: Text | PDF
Research Article Immunology

Follicular regulatory T cells inhibit the development of granzyme B–expressing follicular helper T cells

Abstract

T follicular regulatory (TFR) cells are found in the germinal center (GC) response and help shape the antibody (Ab) response. However, the precise role of TFR cells in the GC is controversial. Here, we addressed TFR cell function using mice with impaired TFR cell development (Bcl6-flox/Foxp3-cre, or Bcl6FC mice), mice with augmented TFR cell development (Blimp1-flox/Foxp3-cre, or Blimp1FC mice), and two different methods of immunization. Unexpectedly, GC B cell levels positively correlated with TFR cell levels. Using a gene profiling approach, we found that TFH cells from TFR-deficient mice showed strong upregulation of granzyme B (Gzmb) and other effector CD8+ T cell genes, many of which were Stat4 dependent. The upregulation of cytotoxic genes was the highest in TFH cells from TFR-deficient mice where Blimp1 was also deleted in Foxp3+ regulatory T cells (Bcl6-flox/Prdm1-flox/Foxp3-cre [DKO] mice). Granzyme B– and Eomesodermin-expressing TFH cells correlated with a higher rate of apoptotic GC B cells. Klrg1+ TFH cells from DKO mice expressed higher levels of Gzmb. Our data show that TFR cells repress the development of abnormal cytotoxic TFH cells, and the presence of cytotoxic TFH cells correlates with a lower GC and Ab response. Our data show what we believe is a novel mechanism of action for TFR cells helping the GC response.

Authors

Markus M. Xie, Shuyi Fang, Qiang Chen, Hong Liu, Jun Wan, Alexander L. Dent

×

Figure 2

TFR cells repress a cytotoxic gene program in TFH cells.

Options: View larger image (or click on image) Download as PowerPoint
TFR cells repress a cytotoxic gene program in TFH cells. WT, Bcl6FC, Bli...
WT, Bcl6FC, Blimp1FC, and DKO mice were immunized twice with PCT (n = 4). Four weeks after the last immunization, TFH cells were isolated by FACS, RNA was then prepared and subjected to RNAseq. (A) Volcano plots showing differentially expressed genes (DEGs) for Bcl6FC versus WT (155 genes up, 410 genes down) and DKO versus Blimp1FC (517 genes up, 1041 down). Blue indicates downregulated genes and purple upregulated genes, using FDR < 0.05 after multiple-test correction and fold change (FC) < –1.8 or > 1.8 (linear). Gzmb is specifically marked in both plots. Gzmb is increased 9-fold in Bcl6FC TFH cells compared with WT TFH cells, and Gzmb is increased 173-fold in DKO TFH cells compared with Blimp1FC TFH cells. (B) Heatmap showing expression assessed with RNAseq of 21 hallmark TFH genes sorted alphabetically. Color scale shows log2RPKM of gene expression. (C) Fraction of genes associated with CD8 (left panel) or Stat4 (right panel) in all TFH expressed genes (gray bar), TFH DEGs upregulated for Bcl6FC (purple bar), or DKO (brown bar) versus WT. The CD8 or Stat4 genes were acquired from published data sets for DEGs in effector CD8 differentiation (18) and Stat4 regulation in Th1 cells (19). The P values were calculated based on hypergeometric distribution, representing statistical significance of enrichment of CD8 and Stat4 genes in Bcl6FC or DKO upregulated DEGs compared with the occurrence in all expressed TFH genes. (D–F) A set of 23 genes was used to create heatmaps based on log2RPKM gene expression for (D) WT, Bcl6FC, Blimp1FC, and DKO TFH cells; (E) naive and effector CD8+ T cells (18); and (F) WT and Stat4–/– Th1 cells (19). In E and F, FCs for the paired sets of genes are shown by a single-column heatmap. See Methods for statistical analysis of gene data sets.