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.
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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

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Figure 5

Cytotoxic gene expression is enriched in Klrg1+ TFH cells.

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Cytotoxic gene expression is enriched in Klrg1+ TFH cells. WT, Bcl6FC, B...
WT, Bcl6FC, Blimp1FC, and DKO mice were immunized with SRBCs and spleens were analyzed for Klrg1 on TFH cell populations by flow cytometry. (A) Analysis of CD4+FOXP3–PD-1+CXCR5+ TFH cells for Klrg1 expression 9 days after immunization. Average Klrg1+ TFH cells are quantitated and graphed as a percentage of TFH cells, and absolute number. n = 4; experiment was repeated 3 times. Cells (100,000 total) were analyzed by flow cytometry and TFH cells (0.5%–3%, 500–3,000) were gated for further analysis. ANOVA with Tukey’s post hoc analysis was used to test for significant differences. (B) TFH cells from 4 DKO mice (n = 3) were separated into Klrg1+ and Klrg– populations by FACS, and RNA was prepared directly after sorting. RT-qPCR was used to analyze gene expression in Klrg1+ and Klrg1– TFH cells. Graphs show relative expression for the indicated genes with the mRNA level in Klrg1– cells set to 1. This experiment was done twice with similar results. Approximately 15,000 Klrg1+ and approximately 500,000 Klrg1– TFH cells were sorted per mouse. Student’s t test was used to detect significant differences.