γδ T cell characterisation in the long term after haematopoietic stem cell transplantation and its impact on CMV control and cGVHD severity

Abstract

Objectives

The clinical outcome after allogeneic haematopoietic stem cell transplantation (aHCT) relies greatly on the efficient recovery of T cells. Several studies have investigated the short-term γδ T cell reconstitution and their role in clinical outcomes following haematopoietic stem cell transplantation. Nevertheless, their long-term characteristics and impact have remained largely unknown.

Methods

We analysed γδ T cells from 20 recipient/donor pairs at phenotypic, clonotypic and functional levels to assess their reconstitution ≥ 8 years (median 18 years) post-transplantation using high-parameter flow cytometry and next-generation sequencing of the TCR γ-chain.

Results

γδ T cells displayed comparable phenotypic characteristics between recipients and matching donors. The Vδ2⁺ subset showed a more activated phenotype and cytokine production, while the Vδ1⁺ and non-Vδ2 T cells maintained long-term CMV control. TCR γ-chain composition in long-term survivors was largely restored, with no significant differences in gene segment usage or diversity. A small cohort of recipients with severe chronic graft-versus-host disease (GVHD) showed overrepresented donor-derived private clonotypes. Furthermore, we also found elevated HLA-DR⁺Vδ1⁺ T cells in recipients with severe chronic GVHD.

Conclusion

Overall, γδ T cells reconstitute with a normalised repertoire, high functional capacity and sustained CMV control ability. An increased proportion of activated Vδ1⁺ T cells correlates with chronic GVHD severity, indicating a potential therapeutic target.