Orphan Nuclear Receptor NR2F6 Suppresses T Follicular Helper Cell Accumulation through Regulation of IL-21

Highlights

• Loss of NR2F6 results in accumulation of Tfh, GC B, and plasma cells after immunization

• Increased GC populations depend on Nr2f6 loss within the CD4 compartment

• NR2F6 directly binds to several sites within the Il21 promoter and CNS −36

• NR2F6 restrains Il21 expression in CD4 cells; IL-21R blockade reduces Tfh accumulation

Summary

CD4 T follicular helper (Tfh) cells are specialized in helping B cells during the germinal center (GC) reaction and ultimately promote long-term humoral immunity. Here we report that loss of the nuclear orphan receptor NR2F6 causes enhanced survival and accumulation of Tfh cells, GC B cells, and plasma cells (PCs) following T cell-dependent immunization. Nr2f6-deficient CD4 T cell dysfunction is the primary cause of cell accumulation. Cytokine expression in Nr2f6-deficient Tfh cells is dysregulated, and Il21 expression is enhanced. Mechanistically, NR2F6 binds directly to the interleukin 21 (IL-21) promoter and a conserved noncoding sequence (CNS) near the Il21 gene in resting CD4⁺ T cells. During Tfh cell differentiation, this direct NR2F6 DNA interaction is abolished. Enhanced Tfh cell accumulation in Nr2f6-deficient mice can be reverted by blocking IL-21R signaling. Thus, NR2F6 is a critical negative regulator of IL-21 cytokine production in Tfh cells and prevents excessive Tfh cell accumulation.