Regulatory T cell therapy is associated with distinct immune regulatory lymphocytic infiltrates in kidney transplants

Adoptive transfer of autologous regulatory T cells (Tregs) is a promising therapeutic strategy aimed at enabling immunosuppression minimization following kidney transplantation. In our phase 1 clinical trial of Treg therapy in living donor renal transplantation, the ONE Study (ClinicalTrials.gov: NCT02129881), we observed focal lymphocytic infiltrates in protocol kidney transplant biopsies that are not regularly seen in biopsies of patients receiving standard immunosuppression.

We present 7 years of follow-up data on patients treated with adoptive Treg therapy early post-transplantation who exhibited focal lymphocytic infiltrates on a 9-month protocol biopsy. We phenotyped their adoptively transferred and peripherally circulating Treg compartments using CITE-seq and investigated the focal lymphocytic infiltrates with spatial proteomic and transcriptomic technologies.

Graft survival rates were not significantly different between Treg-treated patients and the control reference group. None of the Treg-treated patients experienced clinical rejection episodes or developed de novo donor-specific antibodies, and three of ten successfully reduced their immunosuppression to tacrolimus monotherapy. All Treg-treated patients who underwent a protocol biopsy 9 months post-transplantation exhibited focal lymphocytic infiltrates. Spatial profiling analysis revealed prominent CD20⁺ B cell and regulatory (IKZF2, IL10, PD-L1, TIGIT) signatures within cell-therapy-associated immune infiltrates, distinct from the pro-inflammatory myeloid signature associated with rejection biopsies.

We demonstrate for the first time that immune cell infiltrates in transplanted kidneys can occur following adoptive Treg therapy in humans, potentially facilitating within-graft T:B cell interactions that promote local immune regulation.

This work was funded by the 7^th EU Framework Programme, grant/award no. 260687, and the National Institute for Health Research (NIHR).