RIPK1 protects naive and regulatory T cells from TNFR1-induced apoptosis

Jelle Huysentruyt; Wolf Steels; Mario Ruiz Perez; Bruno Verstraeten; Mike Vadi; Tatyana Divert; Kayleigh Flies; Nozomi Takahashi; Bart N Lambrecht; Wim Declercq; Tom Vanden Berghe; Jonathan Maelfait; Peter Vandenabeele; Peter Tougaard

doi:10.1038/s41418-024-01301-w

RIPK1 protects naive and regulatory T cells from TNFR1-induced apoptosis

Cell Death Differ. 2024 May 11. doi: 10.1038/s41418-024-01301-w. Online ahead of print.

Authors

Jelle Huysentruyt^{1

2}, Wolf Steels^{1

2}, Mario Ruiz Perez^{1

2}, Bruno Verstraeten^{1

2}, Mike Vadi^{1

2}, Tatyana Divert^{1

2}, Kayleigh Flies^{1

2}, Nozomi Takahashi^{1

2}, Bart N Lambrecht^{3

4

5

6}, Wim Declercq^{1

2}, Tom Vanden Berghe^{1

2

7}, Jonathan Maelfait^{1

2}, Peter Vandenabeele^{8

9}, Peter Tougaard^{1

2}

Affiliations

¹ Cell death and Inflammation Unit, VIB-UGent Center for Inflammation Research, Ghent, Belgium.
² Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium.
³ Department of Internal Medicine and Pediatrics, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium.
⁴ Laboratory of Mucosal Immunology, VIB-UGent Center for Inflammation Research, Ghent University, Ghent, Belgium.
⁵ Department of Respiratory Medicine, Ghent University Hospital, Ghent, Belgium.
⁶ Department of Pulmonary Medicine, Erasmus MC, Rotterdam, Netherlands.
⁷ Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium.
⁸ Cell death and Inflammation Unit, VIB-UGent Center for Inflammation Research, Ghent, Belgium. Peter.Vandenabeele@irc.vib-ugent.be.
⁹ Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium. Peter.Vandenabeele@irc.vib-ugent.be.

PMID: 38734851
DOI: 10.1038/s41418-024-01301-w

Abstract

The T cell population size is stringently controlled before, during, and after immune responses, as improper cell death regulation can result in autoimmunity and immunodeficiency. RIPK1 is an important regulator of peripheral T cell survival and homeostasis. However, whether different peripheral T cell subsets show a differential requirement for RIPK1 and which programmed cell death pathway they engage in vivo remains unclear. In this study, we demonstrate that conditional ablation of Ripk1 in conventional T cells (Ripk1^ΔCD4) causes peripheral T cell lymphopenia, as witnessed by a profound loss of naive CD4⁺, naive CD8⁺, and FoxP3⁺ regulatory T cells. Interestingly, peripheral naive CD8⁺ T cells in Ripk1^ΔCD4 mice appear to undergo a selective pressure to retain RIPK1 expression following activation. Mixed bone marrow chimeras revealed a competitive survival disadvantage for naive, effector, and memory T cells lacking RIPK1. Additionally, tamoxifen-induced deletion of RIPK1 in CD4-expressing cells in adult life confirmed the importance of RIPK1 in post-thymic survival of CD4⁺ T cells. Ripk1^K45A mice showed no change in peripheral T cell subsets, demonstrating that the T cell lymphopenia was due to the scaffold function of RIPK1 rather than to its kinase activity. Enhanced numbers of Ripk1^ΔCD4 naive T cells expressed the proliferation marker Ki-67⁺ despite the peripheral lymphopenia and single-cell RNA sequencing revealed T cell-specific transcriptomic alterations that were reverted by additional caspase-8 deficiency. Furthermore, Ripk1^ΔCD4Casp8 ^ΔCD4 and Ripk1^ΔCD4Tnfr1^-/- double-knockout mice rescued the peripheral T cell lymphopenia, revealing that RIPK1-deficient naive CD4⁺ and CD8⁺ cells and FoxP3⁺ regulatory T cells specifically die from TNF- and caspase-8-mediated apoptosis in vivo. Altogether, our findings emphasize the essential role of RIPK1 as a scaffold in maintaining the peripheral T cell compartment and preventing TNFR1-induced apoptosis.