Blimp1 regulates the growth and function of human regulatory T cells

Abstract

Abstract Blimp1 is a multifunctional transcriptional regulator that has established roles in mouse T cells. However, its function in human Tregs are not well-understood. To directly evaluate the role of Blimp1 in human Tregs, Blimp1α, the active and dominant isoform of Blimp1, was knocked out in human Tregs in vitro by the Crispr-Cas9 system using dual-targeting sgRNAs. High knockout efficiency was verified at the DNA, RNA, and protein levels. Transcriptome studies identified 356 Blimp1-repressed genes and 399 Blimp1-activated genes in Tregs. The significantly enriched gene sets are associated with cell cycle, apoptosis, cytokine-related signaling, and cytokine production. Consistent with normally restraining Treg growth, functional studies showed that knockout of Blimp1 increased Treg numbers, proliferative responses, and Ki67 expression, but decreased early apoptotic cells. Correspondingly, IL2-induced tyrosine phosphorylation of STAT5 (pSTAT5) was enhanced in Blimp1KO Tregs. Blimp-1 is also positively associated with some aspects of Treg function as loss of Blimp1 downregulated the expression of cytokines, including IL10, IL4, IL5, IL9, IL13, IFNγ, CCL3 and CCL4, and immune checkpoints, including LAG3, PD1, and CTLA4. In the absence of Blimp-1, Foxp3 and Helios levels and IL-6-induced pSTAT3 increased, suggesting a role for Blimp1 in regulating Treg stability. Treg suppressive function, in vitro, however, was not affected by the loss of Blimp1. Collectively, our results suggest that Blimp1 is a pivotal regulator of human Treg growth, function, and stability and is consistent with a model where Blimp1 contributes to Treg homeostasis in vivo. (Supported by R01AI131648). Supported by grant from NIH (R01AI131648).