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

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.