W136 - IL-12 Drives the Differentiation of Human T Follicular Regulatory Cells

Diana Castano – University of Pennsylvania; Sidney Wang – University of Pennsylvania; Hannah Sharpe – University of Pennsylvania; Jacinta Bustamante – INSERM; Emily Yang – Stanford University; Allan Feng – Stanford University; Carole Le Coz – The Children's Hospital of Philadelphia; Neil Romberg – The Children's Hospital of Philadelphia; PJ Utz – Stanford University; Sarah Henrickson – The Children's Hospital of Philadelphia; Jean-Laurent Casanova – The Rockefeller University

Abstract Text: T follicular regulatory (Tfr) cells counteract the B cell-helper activity of T follicular helper (Tfh) cells and hinder the production of antibodies against self-antigens or allergens. A mechanistic understanding of the cues initiating the differentiation of T regulatory (Treg) cells into Tfr cells, which is instrumental for the therapeutic manipulation of diseases associated with a Tfr-imbalance, is still missing. Despite their opposed roles, Tfr and Tfh cell differentiation appears to be controlled by partially overlapping signals, including TCR stimulation and costimulatory molecules. However, it is still unknown if cytokines that have been shown to control the biology of human Tfh cells, including IL-12 and activin A, can influence the differentiation of Tfr cells. To address this question, we evaluated the impact of these two cytokines on the in vitro differentiation of Tfr cells. Herein, we report a role for IL-12 in driving, on activated Treg cells, the induction of molecules that belong to the Tfr cell program, including CXCR5, PD-1, BCL6 and ICOS meanwhile preserving Tfr regulatory function. Conversely, activin A presented a largely negligible effect on the in vitro differentiation of Tfr-like cells and only modestly strengthened the IL-12-driven differentiation of Tfr-like cells. Importantly, patients with inborn errors of immunity in IL12RB1 gene presented with a severe decrease in circulating Tfr cells and produced higher levels of anti-actin autoantibodies in vivo. Overall, this study unveils IL-12 as an inducer of Tfr cell differentiation in vivo and provides a novel approach for the in vitro generation of human Tfr-like cells.