Sonic Hedgehog Is a Determinant of γδ T-Cell Differentiation in the Thymus

Konstantinos Mengrelis,Susan Outram,Anisha Solanki,Susan Ross,Masahiro Ono,Sonia Norris,Tessa Crompton,Ching-In Lau,Jasmine Rowell

doi:10.3389/fimmu.2019.01629

Konstantinos Mengrelis, Susan Outram + Show 7 more

Open Access

https://doi.org/10.3389/fimmu.2019.01629

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Abstract

Here we investigate the function of Hedgehog (Hh) signaling in thymic γδ T-cell maturation and subset differentiation. Analysis of Hh mutants showed that Hh signaling promotes γδ T-cell development in the thymus and influences γδ T-cell effector subset distribution. Hh-mediated transcription in thymic γδ cells increased γδ T-cell number, and promoted their maturation and increased the γδNKT subset, whereas inhibition of Hh-mediated transcription reduced the thymic γδ T-cell population and increased expression of many genes that are normally down-regulated during γδ T-cell maturation. These changes were also evident in spleen, where increased Hh signaling increased γδNKT cells, but reduced CD27-CD44+ and Vγ2+ populations. Systemic in vivo pharmacological Smoothened-inhibition reduced γδ T-cell and γδNKT cells in the thymus, and also reduced splenic γδ T-cell and γδNKT populations, indicating that Hh signaling also influences homeostasis of peripheral γδ T-cell populations. Taken together our data indicate that Sonic Hedgehog is an important determinant of γδ T-cell effector subset differentiation.

Highlights

Gamma delta T-cells are a conserved population of lymphocytes, which like αβ T-cells develop in the thymus. αβ T-cell development and γδ T-cell development diverge at the CD44+CD25+CD4-CD8- stage of thymocyte development, during which rearrangement of β, γ, and δ-chains of the TCR is initiated
Gating on CD3+γδTCR+ thymocytes, we found that ∼5% of thymic γδ T-cells expressed GFP, which reports Hh-mediated transcription (Figure 1B)
As mutation of Hh pathway components caused profound changes in the transcriptional signature of CD27+CD3+γδTCR+ cells in the thymus, and Hh signaling increased the thymic γδNKT population, which migrate to the spleen, we investigated γδ T-cell subsets in the spleen

Summary

Introduction

Gamma delta (γδ) T-cells are a conserved population of lymphocytes, which like αβ T-cells develop in the thymus. αβ T-cell development and γδ T-cell development diverge at the CD44+CD25+CD4-CD8- (double negative [DN2]) stage of thymocyte development, during which rearrangement of β-, γ-, and δ-chains of the TCR is initiated. Successful rearrangement of γ- and δ-chains, and functional expression and signaling though the γδTCR complex drives differentiation into the γδ T-cell lineage, supported by expression of the transcription factor Sox. Cells that have not produced a functional γδTCR, undergo β-selection for differentiation along the αβ T-cell lineage [4, 5]. Γδ T-cells first develop before αβ T-cells during ontogeny, with waves of development leading to distinct subsets of γδ T-cells which home to particular anatomical sites, and use distinct V-γ and V-δ gene segments. These fetal-derived γδ T-cells can be regarded as innate-like cells, which can respond rapidly without clonal expansion.

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