CD161 expression defines new human \u03b3\u03b4 T cell subsets

Amali Karunathilaka,Scott C Bell,Viviana P Lutzky,Andreas Kupz,Patricia Price,John J Miles,Samuel Halstrom,Denise L Doolan,Champa N Ratnatunga,Michael Holt,Rachel M Thomson

doi:10.1186/s12979-022-00269-w

Abstract

γδ T cells are a highly versatile immune lineage involved in host defense and homeostasis, but questions remain around their heterogeneity, precise function and role during health and disease. We used multi−parametric flow cytometry, dimensionality reduction, unsupervised clustering, and self-organizing maps (SOM) to identify novel γδ T cell naïve/memory subsets chiefly defined by CD161 expression levels, a surface membrane receptor that can be activating or suppressive. We used middle-to-old age individuals given immune blockade is commonly used in this population. Whilst most Vδ1+subset cells exhibited a terminal differentiation phenotype, Vδ1− subset cells showed an early memory phenotype. Dimensionality reduction revealed eight γδ T cell clusters chiefly diverging through CD161 expression with CD4 and CD8 expression limited to specific subpopulations. Comparison of matched healthy elderly individuals to bronchiectasis patients revealed elevated Vδ1+ terminally differentiated effector memory cells in patients potentially linking this population with chronic proinflammatory disease.

Highlights

Background γδT cells comprise only 1.5–3% of circulating T cells in humans [1] but 50–70% in ruminants and birds [2, 3], suggesting a pivotal role in host survival
The surface receptor patterns that defineVδ1+ and Vδ1− memory cells Flow-based analyses of Peripheral blood mononuclear cells (PBMCs) samples from 22 healthy individuals revealed a mean γδ T cell, Vδ1+ and Vδ1− of 8.6% (± SD 6%), 30.6% (± SD 27%) and 69.2% (± SD 27%) respectively which are similar to values published for a cohort that included elderly individuals [25]
Four distinct γδ T cell subsets were identified when gating on Vδ1 and CD161 (Fig. 1A), with enumerative means and ± SDs in Vδ1−CD161+cells (53% ± 30%), Vδ1−CD161−cells (12% ± 9%), Vδ1+CD161−(18% ± 23%), andVδ1+CD161+cells (16% ± 20%) determined

Summary

Introduction

Background γδT cells comprise only 1.5–3% of circulating T cells in humans [1] but 50–70% in ruminants and birds [2, 3], suggesting a pivotal role in host survival. We performed a high-dimensional flow analysis with dimensionality reduction and unsupervised clustering of human γδ T cells from middle aged to elderly healthy individuals revealing a novel cell subset network, distorted in bronchiectasis. Detailed phenotypic exploration of cells identified by these two independent methods was performed and findings validated using conventional biaxial gating from original flow data using FlowJo v10.8 (LCC, OR, USA).

Results

Conclusion