One of the greatest challenges in organ and cell transplantation is achieving long-term immune tolerance. Pancreatic islet transplantation can restore near-normal blood glucose regulation in individuals with type 1 diabetes; however, its success is limited by the need for lifelong immunosuppressive therapy, which is associated with significant adverse effects.
Researchers investigated immunotherapeutic strategies for transplanted islets aimed at avoiding long-term immunosuppression. The researchers used nonhuman primates (NHPs) to study how regulatory type 1 T (Tr1) cells interact with effector T cells in the spleen. Their results revealed a previously unknown immune-controlling pathway involving amphiregulin (Areg) and epidermal growth factor receptor (EGFR) signaling, which promotes transplantation tolerance by inducing effector T cell exhaustion.
The study analyzed the frozen splenocytes and peripheral blood lymphocytes of NHPs that had previously received an islet transplant and were categorized as tolerant and nontolerant following withdrawal of immunosuppression. Graft survival in the tolerant group exceeded 365 days, whereas non-tolerant groups had graft survival below 203 days and 150 days, respectively. Profiling of CD4+ T cells by high-dimensional mass cytometry, including donor-specific major histocompatibility complex (MHC) class II tetramers, allowed tracking of allospecific CD4+ T cells.
To determine a regulatory, effector, and exhausted T cell population, computational clustering, trajectory analysis, and cell-cell communication modeling were used. Experimental functional studies were conducted to determine the inhibitory effects of Tr1 cells on effector T cells and involved recombinant Areg stimulation, gene silencing of Areg and Nur77, metabolic experiments, and mixed lymphocyte reactions.
In tolerant animals, 26 CD4+ T cell clusters were identified, showing significant enrichment of regulatory and exhausted subsets in the spleen. Tr1-like clusters were increased 3.4-fold in peripheral blood and 6.5-fold in the spleen compared to controls. One regulatory cluster was 76.3-fold enriched in the spleen, while exhausted T cell clusters were enriched 7.5-fold. Tolerant animals also had more donor-specific CD4+ T cells in the spleen than in blood (0.45% ± 0.12 vs. 0.21% ± 0.02), with these cells showing reduced production of IFN-γ, TNF-α, and IL-17, indicating impaired effector function.
Analysis of cell-cell interaction showed a prominent AregEGFR signaling axis between Tr1 cells and depleted/effector memory T cells in tolerant animals, which was absent in non-tolerant animals. Trajectory analysis indicated that antigen-experienced effector memory cells differentiated into suppressive Areg+ Tr1 and terminally exhausted EGFR+ T cells. Functional studies showed that Areg more than 2-fold enhanced Tr1 differentiation and increased Tr1 populations 3- to 6-fold, and suppressed T cell metabolism and histone acetylation approximately 60-fold. Removal of Areg or Nur77 restored effector T cell proliferation by 40–60%.
This study recognizes the spleen as one significant site for establishing immune tolerance to transplanted islets. These findings indicate that Tr1 cells that produce Areg not only suppress the effector T cells but also actively induce a metabolically suppressed/exhausted phenotype via EGFR signaling. The study demonstrates a correlation between Tr1 cell differentiation and effector T-cell exhaustion, suggesting a tightly integrated regulatory network that promotes long-term, drug-free transplant tolerance. These observations identify the Areg–EGFR pathway as a potential therapeutic target for achieving durable transplant acceptance without prolonged immunosuppression.
Reference: Singh A, Herman A, Dey D, et al. Allospecific splenic Tr1 cells drive effector T cell exhaustion through up-regulated Areg-EGFR signaling to promote transplant tolerance. Sci Adv. 2026;12:eaea0567. doi:10.1126/sciadv.aea0567
