Repertoire diversity and dynamics of peripheral Th17 after allogeneic haematopoietic stem cell transplantation

Summary Th17, a subset of helper T cells that produce interleukin‐17 (IL‐17), is thought to play a pivotal role in the pathogenesis of chronic graft‐versus‐host disease (GVHD). However, the kinetics of Th17 following allogeneic haematopoietic stem cell transplantation (allo‐HSCT) have not been elucidated. In this study, we evaluated the temporal dynamics and diversity of peripherally circulating Th17 after allo‐HSCT. The study included 86 patients who survived without disease relapse for 1 year or more, and for whom peripheral blood samples 3 months after allo‐HSCT were available. Th17 was detected and sorted by flow cytometry, and T‐cell receptor (TCR) repertoire was analysed by a next‐generation sequencing (NGS) method. Patients with chronic GVHD showed a higher TCR repertoire diversity, while those with severe chronic GVHD showed a lower TCR diversity and Th17/Cluster of Differentiation (CD) 4 ratio. The amino acid sequence in complementarity determining region 3 of Th17‐TCR was not apparently different between patients with and without chronic GVHD. Additionally, a higher Th17/CD4 ratio at 3 months was related to a lower incidence of subsequent chronic GVHD. The current study explored the kinetics of peripherally circulating Th17 after allo‐HSCT, which might be associated with the development of chronic GVHD.