Key Points

IL-7R–deficient ETPs have defects in cell cycle and survival.

The most immature Flt3+ ETPs are enriched in IL-7R–expressing cells.

IL-7/IL-7R signaling in the thymus is required to generate Flt3+ ETPs.

Abstract

IL-7 and IL-7R are essential for T lymphocyte differentiation by driving proliferation and survival of specific developmental stages. Although early T lineage progenitors (ETPs), the most immature thymocyte population known, have a history of IL-7R expression, it is unclear whether IL-7R is required at this stage. In this study, we show that mice lacking IL-7 or IL-7R have a marked loss of ETPs that results mostly from a cell-autonomous defect in proliferation and survival, although no changes were detected in Bcl2 protein levels. Furthermore, a fraction of ETPs responded to IL-7 stimulation ex vivo by phosphorylating Stat5, and IL-7R was enriched in the most immature Flt3+Ccr9+ ETPs. Consistently, IL-7 promoted the expansion of Flt3+ but not Flt3− ETPs on OP9-DLL4 cocultures, without affecting differentiation at either stage. Taken together, our data show that IL-7/IL-7R is necessary following thymus seeding by promoting proliferation and survival of the most immature thymocytes.

Footnotes

This work was supported by the Instituto Gulbenkian de Ciência, the Calouste Gulbenkian Foundation, and the Portuguese National Research Council (Fundação para a Ciênciae Tecnologia Grants PTDC/BIA-BID/30925/2017 and PTDC/MED-IMU/3649/2021 to V.C.M.). V.C.M. is supported by Fundação para a Ciência e Tecnologia Contract CEECIND/03106/2018). R.A.P. and C.V.R. are Ph.D. students of the Instituto Gulbenkian de Ciência Integrative Biology and Biomedicine Ph.D. Program and were supported by Fundação para a Ciência e Tecnologia Ph.D. Fellowships PD/BD/114341/2016 and PD/BD/139190/2018, respectively. This work had the support of the research infrastructures Congento LISBOA-01-0145-FEDER-022170 and PPBI-POCI-01-0145-FEDER-022122, both co-financed by Fundação para a Ciência e Tecnologia and Lisboa2020, under PORTUGAL2020 agreement (European Regional Development Fund).

R.A.P. designed the project, designed and performed experiments, analyzed data, and wrote the manuscript; C.V.R. performed experiments, analyzed data, and wrote the manuscript; G.L. performed the scRNA-seq analyses; and V.C.M. designed the project, designed experiments, and wrote the manuscript. All authors edited and contributed to the final version of the manuscript.

The online version of this article contains supplemental material.

Abbreviations used in this article:

γccommon γ-chainCLPcommon lymphoid progenitorDNdouble-negativeEdU5-ethynyl-2′-deoxyuridineeGFPenhanced GFPETPearly T lineage progenitorFMOfluorescence minus oneIGCInstituto Gulbenkian de CiênciaLMPPlymphoid-primed multipotent progenitorRNA-seqRNA sequencingscRNA-seqsingle-cell RNA-seqReceived November 2, 2021.Accepted August 31, 2022.Copyright © 2022 by The American Association of Immunologists, Inc.