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Regulatory T cells (Treg) can regulate alloantigens and may counteract chronic lung allograft dysfunction (CLAD) in lung transplantation. We analyzed Treg in peripheral blood prospectively and correlated percentages of subpopulations with the incidence of CLAD at 2 years. Among lung-transplanted patients between January 2009 and July 2011, only patients with sufficient Treg measurements were included into the study. Tregs were measured immediately before lung transplantation, at 3 weeks and 3, 6, 12, and 24 months after transplantation and were defined as CD4 + CD25 high T cells and further analyzed for CTLA4, CD127, FoxP3, and IL-2 expressions. Between January 2009 and July 2011, 264 patients were transplanted at our institution. Among the 138 (52%) patients included into the study, 31 (22%) developed CLAD within 2 years after transplantation. As soon as 3 weeks after lung transplantation, a statistically significant positive association was detected between Treg frequencies and later absence of CLAD. At the multivariate analysis, increasing frequencies of CD4 + CD25 high CD127 low , CD4 + CD25 high FoxP3 + and CD4 + CD25 high IL-2 + T cells at 3 weeks after lung transplantation emerged as protective factors against development of CLAD at 2 years. In conclusion, higher frequencies of specific Treg subpopulations early after lung transplantation are protective against CLAD development., (© 2016 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Donor alloantigen infusion induces T cell regulation and transplant tolerance in small animals. Here, we study donor splenocyte infusion in a large animal model of pulmonary transplantation. Major histocompatibility complex-mismatched single lung transplantation was performed in 28 minipigs followed by a 28-day course of methylprednisolone and tacrolimus. Some animals received a perioperative donor or third party splenocyte infusion, with or without low-dose irradiation (IRR) before surgery. Graft survival was significantly prolonged in animals receiving both donor splenocytes and IRR compared with controls with either donor splenocytes or IRR only. In animals with donor splenocytes and IRR, increased donor cell chimerism and CD4(+) CD25(high+) T cell frequencies were detected in peripheral blood associated with decreased interferon-γ production of leukocytes. Secondary third-party kidney transplants more than 2 years after pulmonary transplantation were acutely rejected despite maintained tolerance of the lung allografts. As a cellular control, additional animals received third-party splenocytes or donor splenocyte protein extracts. While animals treated with third-party splenocytes showed significant graft survival prolongation, the subcellular antigen infusion showed no such effect. In conclusion, minipigs conditioned with preoperative IRR and donor, or third-party, splenocyte infusions may develop long-term donor-specific pulmonary allograft survival in the presence of high levels of circulating regulatory T cells., (© Copyright 2015 The American Society of Transplantation and the American Society of Transplant Surgeons.)

CD4(+)CD25highFOXP3(+) regulatory T cells (Tregs) can control allospecific immune responses in vitro and in titrated lymphopenic transplantation models. However, under non-lymphopenic conditions, as seen in patients with autoimmune diseases or after organ transplantation, polyspecific Tregs so far have been largely ineffective to control immune responses in animal models. Yet currently polyspecific CD4(+)CD25high Tregs are being tested in clinical trials. Donor materials are usually limited for the generation of donor-specific Tregs. Herein we have developed a method to produce large quantities of activated donor B cells by stimulation of donor peripheral blood mononuclear cells with 3T3 fibroblasts expressing CD40L. These activated donor B cells are potent stimulators of CD4(+)CD25high Tregs, which were expanded efficiently to inhibit an allo-MLR in donor-specific fashion. They were far more potent in inhibiting alloimmune responses in humanized mice compared with the polyspecific CD4(+)CD25high Tregs. Generation of donor-specific Tregs could be performed under good manufacturing practice conditions. Donor-reactive Tregs may be a valuable tool to control immune responses after transplantation a setting in which polyspecific Tregs have failed to date., (Copyright © 2013. Published by Elsevier Inc.)