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Introduction: donor-derived modified immune cells (MIC) induced long-term specific immunosuppression against the allogeneic donor in preclinical models of transplantation. In a phase I clinical trial (TOL-1 Study), MIC treatment resulted in a cellular phenotype that was directly and indirectly suppressive to the recipient's immune system allowing for reduction of conventional immunosuppressive therapy. Here, we describe a protocol for a randomised controlled, multicentre phase-IIb clinical trial of individualised immunosuppression with intravenously administered donor MIC compared with standard-of-care (SoC) in living donor kidney transplantation (TOL-2 Study). Methods and analysis: sixty-three living donor kidney transplant recipients from six German transplant centres are randomised 2:1 to treatment with MIC (MIC group, N=42) or no treatment with MIC (control arm, N=21). MIC are manufactured from donor peripheral blood mononuclear cells under Good Manufacturing Practice conditions. The primary objective of this trial is to determine the efficacy of MIC treatment together with reduced conventional immunosuppressive therapy in terms of achieving an operational tolerance-like phenotype compared with SoC 12 months after MIC administration. Key secondary endpoints are the number of patient-relevant infections as well as a composite of biopsy-proven acute rejection, graft loss, graft dysfunction or death. Immunosuppressive therapy of MIC-treated patients is reduced during follow-up under an extended immunological monitoring including human leucocyte antigen-antibody testing, and determination of lymphocyte subsets, for example, regulatory B lymphocytes (Breg) and antidonor T cell response. A Data Safety Monitoring Board has been established to allow an independent assessment of safety and efficacy. Ethics and dissemination: ethical approval has been provided by the Ethics Committee of the Medical Faculty of the University of Heidelberg, Heidelberg, Germany (AFmu-580/202, Preparation of the study was funded by the Federal Ministry of Education and Research, Berlin, Germany (FKZ 161B0560A, 161B0560B, and FKZ 031B0560A, 031B0560B), and TolerogenixX GmbH, Heidelberg, Germany (N/A). Conduct of the study is funded by TolerogenixX GmbH (N/A).

Studies of the effect of minor H antigen mismatching on the outcome of renal transplantation are scarce and concern mainly single center studies. The International Histocompatibility and Immunogenetics Workshops (IHIW) provide a collaborative platform to execute crucial large studies. In collaboration with 16 laboratories of the IHIW, the role of 15 autosomal, 10 Y-chromosome encoded minor H antigens and 3 CD31 polymorphisms, was investigated in relation to the incidence of renal graft rejection and graft loss in 444 human leukocyte antigens (HLA)-identical sibling renal transplantations. Recipient and donor DNA samples were genotyped for the minor H antigens HA-1, HA-2, HA-3, HA-8, HB-1, ACC-1, ACC-2, SP110, PANE1, UGT2B17, C19Orf48, LB-ECGF-1, CTSH, LRH-1, LB-ADIR and HY. The correlation between minor H antigen mismatch and the primary outcome graft rejection or graft loss was statistically analyzed. The incidence of rejection was very low and no correlation was observed between one or more minor H antigen mismatch(es) and a rejection episode (n = 36), of which only eight resulted in graft loss. In summary, in our study cohort of 444 renal transplants, mismatching for neither autosomal nor HY minor H antigens correlate with rejection episodes or with graft loss.

The incidence of gastric, colonic, and rectal cancers was determined in a cohort of 73,076 men and women chronically immunosuppressed after heart or renal transplantation, to test the hypothesis that there would be a reduced incidence of gastric cancer by dampening chronic gastritis secondary to infection caused by Helicobacter pylori. Follow-up was from 1-13 years. No change in the incidence of gastric cancer was found (32 cases observed, 32.86 expected). An increase in colon cancer was found (75 cases observed, 62.27 expected). A significant reduction in the incidence of rectal cancer was found (15 cases observed, 41.5 expected). This led to a chi2 of 16.92 with 1 degree of freedom, significant at the 0.1% level. The effect was greater in men than women and more marked in heart recipients than in those receiving renal transplants. This unexpected finding led to a review of experiments in mice and rats that present evidence for immune promotion of large-bowel cancers induced by carcinogens by gut-associated lymphoid tissue. We conclude that an analysis of immune function in gut-associated lymphoid tissue in the stomach, colon, and rectum in healthy and immunosuppressed patients may lead to a better understanding of immunosurveillance in the colon and immune promotion of rectal cancers.