Non-canonical NFKB signaling endows suppressive function through FOXP3-dependent regulatory T cell program

Regulatory T cells (Tregs) play a central role in modulating adaptive immune responses in humans and mice. The precise biological role of non-canonical nuclear factor 'kappa-light-chainenhancer' of activated B cells (NFKB) signaling in human Tregs has yet to be fully elucidated. To gain insight into this process, a Treg-like cell line (MT-2) was genetically modified using CRISPR/ Cas9. Interestingly, NFKB2 knockout MT-2 cells exhibited downregulation of FOXP3, while NFKB1 knockout did not. Additionally, mRNA expression of FOXP3-dependent molecules was significantly reduced in NFKB2 knockout MT-2 cells. To better understand the functional role of the NFKB signaling, the NFKB1/NFKB2 loci of human primary Tregs were genetically edited using CRISPR/Cas9. Similar to MT-2 cells, NFKB2 knockout human Tregs displayed significantly reduced FOXP3 expression. Furthermore, NFKB2 knockout human Tregs showed downregulation of FOXP3-dependent molecules and a diminished suppressive function compared to wild-type and NFKB1 knockout Tregs. These findings indicate that non-canonical NFKB signaling maintains a Treg-like phenotype and suppressive function in human Tregs through the FOXP3-dependent regulatory T cell program.