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 6

Increased GC B cell apoptosis in TFR-deficient mice.

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Increased GC B cell apoptosis in TFR-deficient mice. WT, Bcl6FC, Blimp1F...
WT, Bcl6FC, Blimp1FC, and DKO mice were immunized with SRBCs and spleen cells were analyzed by flow cytometry for B220+CD38–GL7+ GC B cells. (A) Representative flow plots are shown. (B and C) The relative decrease of GC B cells in Bcl6FC and DKO mice is graphed with (C) Bcl6FC mice compared with WT mice, and (D) DKO mice compared with Blimp1FC mice. GC B cell percentages were normalized to average control (WT in B, Blimp1FC in C) GC B cell percentages. Individual GC B cell gain or decrease was determined by the following formula: ([average control % – normalized individual %]/average control %) × 100, with a positive value equaling loss and a negative value equaling gain. n = 8; data in B and C are combined from 2 different experiments. Student’s t test was used to detect significant differences. (D) Annexin V+ GC B cells in WT, Bcl6FC, Blimp1FC, and DKO mice, 3 days after immunization. Flow plots show GC B cells gated as in A. Graphs show average annexin V+ GC B cells. n = 4; experiment was repeated 3 times; representative data are shown. ANOVA with Tukey’s post hoc analysis was used to test for significant differences.