AUTHOR=Urbano Paulo C. M. , He Xuehui , Heeswijk Bennie van , Filho Omar P. S. , Tijssen Henk , Smeets Ruben L. , Joosten Irma , Koenen Hans J. P. M. 

TITLE=TNFα-Signaling Modulates the Kinase Activity of Human Effector Treg and Regulates IL-17A Expression

JOURNAL=Frontiers in Immunology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2019.03047

DOI=10.3389/fimmu.2019.03047

ISSN=1664-3224

ABSTRACT=<p>Maintenance of regulatory T cells CD4<sup>+</sup>CD25<sup>high</sup>FOXP3<sup>+</sup> (Treg) stability is vital for proper Treg function and controlling the immune equilibrium. Treg cells are heterogeneous and can reveal plasticity, exemplified by their potential to express IL-17A. TNFα-TNFR2 signaling controls IL-17A expression in conventional T cells via the anti-inflammatory ubiquitin-editing and kinase activity regulating enzyme <italic>TNFAIP3/</italic>A20 (tumor necrosis factor-alpha-induced protein 3). To obtain a molecular understanding of TNFα signaling on IL-17 expression in the human effector (<sub>eff</sub>Treg, CD25<sup>high</sup>CD45RA<sup>−</sup>) Treg subset, we here studied the kinome activity regulation by TNFα signaling. Using FACS-sorted naïve (<sub>naïve</sub>Treg, CD25<sup>high</sup>CD45RA<sup>+</sup>) and <sub>eff</sub>Treg subsets, we demonstrated a reciprocal relationship between TNFα and IL-17A expression; <sub>eff</sub>Treg (TNFα<sup>low</sup>/IL-17A<sup>high</sup>) and <sub>naïve</sub>Treg (TNFα<sup>high</sup>/IL-17A<sup>low</sup>). In <sub>eff</sub>Treg, TNFα-TNFR2 signaling prevented IL-17A expression, whereas inhibition of TNFα signaling by clinically applied anti-TNF antibodies led to increased IL-17A expression. Inhibition of TNFα signaling led to reduced <italic>TNFAIP3</italic> expression, which, by using siRNA inhibition of <italic>TNFAIP3</italic>, appeared causally linked to increased IL-17A expression in <sub>eff</sub>Treg. Kinome activity screening of CD3/CD28-activated <sub>eff</sub>Treg revealed that anti-TNF-mediated neutralization led to increased kinase activity. STRING association analysis revealed that the TNF suppression <sub>eff</sub>Treg kinase activity network was strongly associated with kinases involved in TCR, JAK, MAPK, and PKC pathway signaling. Small-molecule-based inhibition of TCR and JAK pathways prevented the IL-17 expression in <sub>eff</sub>Treg. Together, these findings stress the importance of TNF-TNFR2 in regulating the kinase architecture of antigen-activated <sub>eff</sub>Treg and controlling IL-17 expression of the human Treg. These findings might be relevant for optimizing anti-TNF-based therapy and may aid in preventing Treg plasticity in case of Treg-based cell therapy.</p>